WATER   PURIFICATION 

AND 

SEWAGE   DISPOSAL 


WATER    PURIFICATION 

AND 

SEWAGE    DISPOSAL 


BY 

DR.   J.    TILLMANS 

DIRECTOR    OF    THE    CHEMICAL    DEPARTMENT    OF    THE 
MUNICIPAL    INSTITUTE    OF    HYGIENE,    FRANKFORT-ON-MAINE 


TRANSLATED   BY 

HUGH  S.  TAYLOR,  M.Sc 


UNIVERSITY    OF    LIVERPOOL 


With  2 1  Illustrations  in  the  Text 


NEW   YORK 

D.   VAN   NOSTRAND   CO. 

TWENTY-FIVE  PARK  PLACE 

19*3 


PREFACE 

TO  THE  ENGLISH  TRANSLATION 

SINCE  the  recognition  of  their  significance  in  the  promotion  of  the 
public  health,  methods  of  water  purification  and  sewage  disposal 
have  earned  a  steadily  increasing  importance.  Consequently, 
these  branches  of  industry  have  enjoyed  the  most  zealous  atten- 
tion of  the  scientist  and  of  the  engineer. 

I  have  endeavoured  in  the  present  monograph  to  give  a  survey, 
short  perhaps,  but  as  complete  as  possible,  of  the  present 
position  in  regard  to  Water  Purification  and  Sewage  Disposal. 

Owing  to  the  wide  range  of  this  subject  particular  processes 
could  only  be  treated  shortly  in  the  space  at  disposal. 

One  chapter,  which  is  very  fully  treated  in  the  present  volume, 
though  slightly  elsewhere,  is  the  disposal  of  industrial  sewage. 
Many  of  the  processes  of  purification  are  of  quite  recent  date, 
and  fresh  experience  is  being  obtained  daily  and  reported  upon 
in  the  most  diverse  publications.  I  have  endeavoured  to  collect 
such  information. 

In  the  translation  some  small  changes  and  additions  have  been 
made  in  the  chapters  on  sand  filtration,  the  removal  of  manganese, 
and  Travis  and  Emscher  wells. 

The  extensive  literature  supplied  in  the  German  original,  which 
served  as  the  basis  in  the  composition  of  the  book,  has  not  been 
printed  in  the  English  translation,  as  it  treats  in  the  main  of 
German  literature. 

THE   AUTHOR. 

FRANKFORT-ON-MAINE, 
October,  1912. 


TRANSLATOR'S   PREFACE 

ENGLAND,  as  the  author  points  out,  is  the  classic  country  for 
sewage  disposal.  As  a  consequence,  the  translation  of  a  book 
on  the  subject  of  water  purification  and  sewage  disposal  from  the 
German  point  of  view,  might  at  first  sight  seem  unnecessary. 
It  is  to  be  hoped,  however,  that  a  study  of  the  present  volume 
will  prove  that  view  to  be  incorrect.  The  careful  attention  which 
has  been  paid  by  the  German  authorities  during  the  past  few 
decades  to  the  provision  of  suitable  water  supplies  and  the 
adequate  disposal  of  sewage,  renders  the  present  critical  survey 
of  modern  methods  at  once  interesting  and  useful  to  the  English 
reader.  Especially  should  this  be  true  of  the  chapter  on  the  dis- 
posal of  industrial  sewage. 

I  have  to  express  my  thanks  to  the  author,  Dr.  Tillmans,  for 
a  revision  of  the  present  text,  and  to  Messrs.  Hubers  and  Mond. 
I  desire  also  to  record  my  indebtedness  to  my  friends  Mr.  J.  W. 
Yates,  M.Sc.,  and  Mr.  A.  Shacklady,  B.Sc.,  for  valuable  guidance 
and  assistance  in  the  correction  of  the  proofs. 

HUGH   S.   TAYLOR. 

LIVERPOOL, 

October,  1912. 


vn 


TABLE    OF   CONTENTS 

WATER  PURIFICATION. 
GROUND-WATER,  SPRING-WATER,  SURFACE-WATER. 


3  AC; 


A.  Purification  of  Water  for  Drinking  Purposes        .         .         .         .         .  2 

Bacteria  and  disease  germs  in  water     .        j.                 .         ...  2 

I.  PURIFICATION  OF  WATER   FOR  DRINKING  PURPOSES  ON  A 

LARGE  SCALE     .       .       ,      ••;_"...    .       .       .       .       .  :     .  4 

(i)  Filtration  Processes     .    .    .  •     .       .        .       .       .       .  4 

(a)  Slow  sand  filtration           .         .         .         .         . .       ...  5 

Preparation,  composition,  and  working  of  the  filter .         .  5 
Uniformity  of  the  sand,  filtration  pressure,  covered  and 

uncovered  filters    .         .         ... 6 

Washing  and  renewal  of  the  sand     .         .         r        .         .  7 
Filter    film,    filtration    pressure,    P>ankel   and   Piefke's 
fundamental  investigations,  double  filtration  according 
to    Gotze,   and    preliminary    filtration,    Puech-Chabal 

system  .         .   '      .         .         .         .         ,         .        .         .  8 

Cost ;  control  by  estimation  of  the  germ-content      .         .  9 
(ti)  Percolating  sand  filters     .         .         ....         .         .10 

(c]  Mechanical  filters     .         «         . 10 

Nature  and  control  of  the  mechanical  filter,  old  and  new 

systems.         .         .         .         .         .    .  *•.  .•        .         .         .  11 

The  Jewell  Export  Mechanical  Filter       .         .         .         .  11 

Experience  with  the  Jewell  Export  Mechanical  Filter      .  13 

(d)  Artificial  preparation  of  ground-water  from  surface-water  14 

Natural  bank  filtration,  infiltration 14 

Application  of  the  process  in  various  towns      .         .         .16 
(e)  Importance  of  water  filtration   in  the   maintenance   of 
public  health,  and  a  critical  examination  of  the  value  of 

sand  and  mechanical  filtration      .         .         .         .         .  16 

(ii)  Sterilisation  Processes        .  .18 

(</)  The  Ozone  Process  .  .  .18 

Siemens' Ozone  plant  at  St.  Petersburg  .  .  20 

Investigations  on  the  action  of  Ozone  .  .  .  .  22 

(/*)  The  Ferric  Chloride  Process 24 


TABLE   OF   CONTENTS 

PAGE 

(c)  The  Chloride  of  Lime  Process 25 

Nature  and  cost  of  the  process          .         .         .         .  "     .       25 
Investigation  and  review  .         .         .         .         ...       26 

(d)  Ultra-violet  light :       27 

The  investigations  of  Courmont  and  Nogier    .         .         .27 
The  investigations   of  the   Konigl.   Prufungsanstalt  fiir 

Wasserversorgung    (Imperial    Institute   of  Tests  for 

Water  Supply)  (Grimm  and  Weldert)  .         .         .  .28 

Other  authors  on  the  process .28 

Comparison  of  the  costs  of  filtration  and  sterilisation  .       29 

(e)  Disinfection  of  water-mains  and  wells      .         .         .  '3° 

(iii)  Purification   of  Water  in  other  Directions  than  of 

Health ....      30 

(a)  Removal  of  iron        .         .         .         .         .         ...         .  30 

Disadvantages  of  water  containing  iron  ;  nature  of  the 

processes  for  removing  iron  .         .         .         .         .         .  31 

The  most  important  methods  of  iron-removal  .         .         .  32 

Open  and  closed  iron-removal  plants       .         .        .         .  33 

Method  of  working  ;  cost          .         ...         .         .34 

(ft)  Removal  of  manganese     .         .         .                 t         .        .  35 
Disadvantage    of   water    containing    manganese ;    the 
Breslau    calamity  ;    different    methods    of   removing 

manganese 35 

(c)  Removal  of  free  carbon  dioxide 36 

Corrosive  action  of  water  containing  carbon   dioxide  ; 
removal  by  limestone  ;  description  of  the  Frankfort 

plant '37 

Removal  with  caustic  soda  or  sodium  carbonate      .         .  38 

Removal  by  aeration  ;  vacuum  process     .         .       • . .       .  40 

II.  PURIFICATION  OF  DRINKING-WATER  ON  A  SMALL  SCALE      .      40 

Basic  disadvantages  of  the  purification   of  drinking-water 
on  a  small  scale,  as  opposed  to  large-scale  operations        .       40 

(i)  Small  or  Household  Filters 41 

More  or  less  uncertain  action  of  all  small  filters   .         .         -41 

(a)  Charcoal  filters 41 

(b)  Stone  filters 42 

(c)  Asbestos  filters     ...  ....       42 

(rt)  Clay  filters  .         .  -42 

(e)  Earthenware  filters  .       42 

(/)  Kieselguhr  filters  .       43 

(ii)  Boiling  the  Water       .  45 

Apparatus  for  boiling  large  quantities  of  water      ...       45 
Advantages    and    disadvantages    of    boiling   the   water   as 
compared  with  household  filters 46 


TABLE   OF   CONTENTS  xi 


PAGE 


(iii)  Small  Ozone  Plants  and  Ultra- Violet  Light  Apparatus      4? 

Stationary  and   transportable   ozone   plants,    Siemens   and 

Halske 47 

Experiments  with  household  apparatus          ....       48 

(iv)  Removal  of  Iron  from  Single  Wells  .  .  .  -49 
Different  methods  of  removing  iron  from  single  wells  .  .  49 
Bastard  pump  of  Deseniss  and  Jacobi  .....  5° 

B.  Purification  of  Water  for  Technical  Purposes      .         .         .         .  5 1 

Requirements  of  a  water  used  for  industrial  purposes  .         .  51 
Softening  of  boiler-feed  water,  temporary  hardness,  perma- 
nent hardness,  degree  of  hardness     .         .         .         .         .  52 

Softening  by  the  lime-soda  process  :  method,  estimation  of 

the  amount  to  be  added      .         .         .         .         ...  53 

Description  of  a  lime-soda  softening  plant  (Voran  system)  .  55 

Advantages  and  disadvantages  of  the  lime-soda  process       .  58 

The  Reisert  Baryta  Process -59 

Advantages  and  disadvantages  of  the  Baryta  Process  .         .  59 

The  Permutit  Process  :  method,  advantages,  disadvantages  60 
Importance  of  an  intelligent  supervision  of  softening  plants, 

so-called  boiler  scale  preventatives 61 

SEWAGE    DISPOSAL. 

The  significance  of  river  pollution  and  the  importance  of 
sewage  disposal  .         .         .         .      •  .         .         .         .         .63 

Self-purification  of  rivers        v 65 

Domestic  and  industrial  sewage     ...         .         .         -67 

A.  Purification  of  Domestic  Sewage    .        ..'....         .         .         .       67 

The  different  processes  .         .        -.         .         .         .         .         .68 

I.  MECHANICAL  PURIFICATION  OF  SEWAGE    .        .        .        .        .68 
(i)  Screens,  Rakes,  and  Sieves         ;        .        .        .        .        .      68 

Coarse  and  fine  screens,  stationary  and  movable  rakes  .  69 
Uhlfelder's  revolving  screen  ;  the  Rien  sieve  ...  69 

(ii)  Grease  Separators 72 

Kremer  apparatus .         .         .72 

Kremer  septic  wells  ;  other  grease  separators  73 

(iii)  Grit  Chambers     ....  73 

(iv)  Sedimentation  Tanks  and  Wells 74 

P'orm  of  sedimentation  tanks  ;  velocity  of  sedimentation  .  74 
Sludge  disposal  :  addition  of  chemicals  ....  76 
Clarification  effect,  sedimentation  wells,  towers  .  .  -77 


xii  TABLE   OF   CONTENTS 

PAGE 

(v)  Septic  Tanks .78 

Method  ;  sludge  and  removal  of  sludge  ;  advantages  and 

disadvantages  of  septic  tanks 78 

(vi)  Travis  and  Emscher  Wells 79 

Method;  Travis  tank .  ...     .  79 

Emscher  wells 82 

Critical  review .         .         .83 

II.    DEGENER'S  COAL-PULP  PROCESS 84 

III.    BIOLOGICAL  PURIFICATION  OF  SEWAGE  .        .        .        .     •  >.  84 

(i)  The  Artificial  Biological  Process         .       .       .        .       .  85 

Method           ...        .        .        .     .  .        .        .        .  85 

Sewage    disposal     in    England,    Preliminary    purification, 
Material  of  the  biological  beds,  Contact  beds,  Percolat- 
ing filters     .         .         ....••..        .         .         .         .        .         .  85 

Cost        .         .         .         ."  .  .        ...        .        .        .  89 

Theories   as   to    the    nature    of  biological    purification   of 

sewage  (Brettschneider,  Travis,  Dunbar)          .         .         .  89 

(ii)  Land  Treatment ;  Broad  Irrigation  .        .       ,       .        .  9° 

(a)  Sewage  Farming     .         .         .         .         .         *        .  90 

Nature,    good    and  bad   soils   for   irrigation   purposes, 

irrigation  of  sloping  surfaces         .      '' -.        .         .        .  9° 

Irrigation  of  beds      .         .         .        .         .        .        .         .  90 

Eduardsfeld  Process          .         .        .         .         .        .      .  .  91 

Action  of  the  irrigation     .         .         .         .         .        .         .  92 

Importance  of  preliminary  treatment       .        .         .         .  92 

Various  details  on  suitable  methods  of  treatment    .         .  92 

Impregnation  permissible,  rent  and  cost  .         -.      •.        .  93 

(ff)  Intermittent  Sand  Filtration    .         .        *         .        .        .  94 

Historical  distinction  from  broad  irrigation      .        .         .  94 

Experience  with  the  process  in  Massachusetts,  U.S.A.   .  94 

(iii)  Purification  of  Sewage  with  Fish-ponds  .       .        . .      .  96 

IV.  DISPOSAL  AND  PROFIT  FROM  THE  RESULTING  RESIDUES     .  97 

(i)  Grit-Chamber  Residues,   Residues  from  Screens,  Sedi- 
mentation Sludge 97 

(ii)  Drying  of  the  Sludge   .  -99 

Disposal  on  the  land      .         .         .         .         .         .  99 

Contents  of  Emscher- well  sludge 100 

Drying  in  ditches '  .         .  100 

Filter-presses          .........  100 


TABLE   OF   CONTENTS  xiii 

PAGE 

Schafer-ter-Mer  Centrifuge    .  101 

Disposal  in  the  sea         .  •  102 

Addition  of  nitrates       ...  .  104 

Cost  of  the  various  processes  .  104 

(iii)  Profit  from  Sludge       .  .104 

As  manure .•     „    •  104 

Preparation  of  artificial  manure     .         .         .  .         .  105 

Recovery  of  grease        .  .  .  105 

Generation  of  electrical  energy  by  burning  .         .         .;       .  107 

Frankfort  sludge  disposal       .         .  .         .         ...  107 

Gasification  of  sludge     .        .        ,        .        ...•''.        .  108 

B.   The  Purification  of  Industrial  Sewage  .  .         .     109 

I.  GENERAL         ....  .109 

Reception  into  the  town's  sewers  .         ,*        .-       .         .         .109 
Leakages,  condenser  waters,  and  effluents  from  particular 
manufacturing  processes.     Association  of  sewage  from 
different  processes     ....         .  '  .         .     1 10 

Reservoirs,  filters   .        ...         .         .         .         .         .     1 1 1 

Use  of  industrial  sewage  for  laying  dust  on  the  roads  .         .     1 1 1 

II.  THE  PURIFICATION. OF  INDUSTRIAL  SEWAGE  IN  DETAIL       .     112 

Classification  of  industrial  sewage         .  .  .  .  .112 

1.  Cloth  factories    .         .         .         .  .  .  .  .    '  .     113 

2.  Cardboard  works        .         .         .  .  f  .  .  .113 

3.  Straw-board  works     ,                 .  ....  .114 

4.  Mines  (coal-washing)         ..         .  .  .  .  .     114 

5.  Sewage  from  works  granulating  slag  .  ;  .  .     114 

6.  Paper  and  cellulose  mills  .         .  .  .  .  ..115 

7.  Breweries  ......  .  .  .117 

8.  Tanneries  .         .         .         .  .     ..  .  .:"•'  .118 

9.  Dairies  and  margarine  works     .  .  .  .  .  .     119 

10.  Slaughter-houses,  knackers' yards,  glue  works  .         .  .     120 

11.  Sugar  works       .         .   '     .        \         .      ,  .         .         .  .     120 

12.  Starch  works      .                                   ...  .122 

13.  Distilleries,  yeast  works     .         .         .         .         ,         .  .123 

14.  Sour-krout  works       ...         .         .         .  .      123 

15.  Dye  works  and  print  woiks        .         .         ...         .  .     123 

16.  Chemical  works          .         .         .               ...         .  .     125 

17.  Bleach  works     .         .         .         .      ' 126 

18.  Gas  works           ..*      .     •    ,         .                  ...  .     126 

19.  Ammonia  works         .  ......     127 

20.  Potash  works     .         .         .         .         .         .                  .  .127 

21.  Metal  works  and  works  manufacturing  mordants     .  .128 

22.  Manufactories  of  photographic  material  and  paper  %  .128 


xiv  TABLE    OF   CONTENTS 

PAGE 

23.  Sewage  containing  cyanides      .         .         .         .         .         .129 

24.  Wool-scouring,  wool-combing,  and  wool-finishing     .         .130 

25.  Petroleum  refineries  .         .         .         .         .         .         .         .130 

26.  Sewage  containing  soaps    .  .         .         .         .         .     131 

27.  Oil  works 132 

C.    The  Disinfection  of  Sewage  .         .         .         .         .         .         .132 


LIST  OF  AUTHORS     .  .135 

LIST  OF  LOCALITIES  .                                       .                       ...     137 
INDEX  OF  SUBJECTS  .  138 


TABLE   OF   EQUIVALENTS    IN   WEIGHTS 
AND    MEASURES. 

i   metre=io  decimetres  =  100  centimetres  =  1000   millimetres  =  1*093   yards  = 

3-28  feet  =  39-37  ins. 

i  cubic  metre  =  1000  litres  =  1-308  cubic  yards  =  35*3  cubic  feet  =  220  gallons. 
i  kilogram  =  2 '2046  Ibs.     1000   kilograms  =  approximately   i   ton.     i    gram  = 

1 5 '43  grains. 


LIST  OF  ILLUSTRATIONS 


PAGE 


Fig.     r.     Diagrammatic  Representation  of  a  Sand  Filter       .  6 

,,      2.     The  Jewell  Export  Mechanical  Filter        .  '  .  .       :.       12 

„      3.     Diagrammatic  View  of  the  Ozone  Waterworks  at  St.  Petersburg       19 

„      4.     Ozone  Waterworks,  St.  Petersburg.     Sterilisation  Towers  and 

Emulsifiers  .  .  -.  ...         .20 

,,      5.     Ozone  Waterworks,   St.  Petersburg.     Batteries  for   the  Ozone 

apparatus               '.                 .                 .                 .  ..'       .       21 

„      6.     Open  Iron-removal  Plant,  "Voran"  System  .         •       34- 

,,      7.     Closed  Iron-removal  Plant,  "Voran"  System  .       34 

„      8.     Acid  Neutralisation  Plant  in  the  Saxony  Deep  Reservoir  .         .       39 

„      9.     Berkefeld  Filter            .  '              .  ..44 

„    10.     Apparatus  for  Boiling  Water  of  the  Firm  of  Aug.  Schmidt  and 

Sons,  Hamburg-Uhlenhorst     .....  .  .         -46 

„  ii.  Bastard  Pump  of  Deseniss  and  Jacobi      .  .  .  .50 

„  12.  Lime-Soda  Softening  Plant,  "  Voran "  System  .  .       56 

„  13.  Uhlfelder's  Revolving  Screen     .                 .    •  .  •.  .       69 

,,  14.  Rien  Sieve    .                 .                 .                 .  ..  .  .       70 

„  15.  Kremer  Apparatus        .                  .                 .  .  .  .       71 

„  16.  Grease  Separators  of  the  "  Stiidtereinigung  Firm,"  Berlin- 
Wiesbaden  .  .  .  ....  72 

,.    17.     Frankfort  Sedimentation  Tank  (Cross  Section)        .  -.         .       75 

.,  1 8.  Clearing  Well  Installation  at  Norwich  on  the  Travis  Hydro- 
lytic  System,  with  Colloider  hung  in.  From  "  Wasser  und 
Abwasser,"  1909-10,  vol.  II,  p.  71  .  .  80 

,,    19.     Emscher  Wells  .  .  .  .  81 

.,    20.     Sludge  Centrifuge  :  Schafer-ter-Mer  System  .  .         .102 

„     21,  „  „  „  I03 


WATER    PURIFICATION 


THE  water  present  on  the  earth  is  engaged  in  a  continuous 
circulatory  process. 

It  evaporates  from  the  oceans,  seas,  rivers,  etc.,  and  passes  into 
the  atmosphere  as  water- vapour.  In  the  higher  strata  it  condenses 
to  form  clouds,  and  then  returns  to  the  earth's  surface  as  rain, 
snow,  hail,  and  dew. 

A  part  of  this  water  evaporates  immediately,  another  part 
flows  away  to  the  nearest  surface  reservoirs.  A  third  part,  on  the 
contrary,  penetrates  into  the  earth's  crust,  and  sinks  deeper  and 
deeper  until  it  reaches  an  impermeable  stratum,  whereupon  it 
collects  and  fills  the  pores  and  hollows  of  the  overlying  ground. 
This  water  is  called  ground-water.  Volger  considers  ground- 
water  as  a  product  of  the  condensation  of  ground-vapours,  and 
Mezger  assumes  that  it  is  the  vapours  rising  from  the  depths 
which  condense.  According  to  Novak  it  mainly  results  from 
the  water  of  the  oceans  penetrating  into  the  interior  of  the  earth. 
Although  ground-water  may  receive  considerable  additions  from 
one  or  other  of  these  sources,  still  it  must  originate  in  greater 
part  in  the  first-mentioned  manner,  through  infiltration.  From 
the  impermeable  layer  it  passes  along  very  slowly  to  the  nearest 
lower-lying  waters. 

Spring -water  is  a  mountain  ground -water  which,  owing 
to  this  movement,  makes  its  appearance  in  a  cleft  of  the 
mountain. 

In  contradistinction  to  ground-water,  all  water  which  remains 
in  contact  with  the  outer  air  is  designated  as  surface-water. 
Surface-water  is  therefore  the  water  of  seas,  rivers,  ponds, 
cisterns,  dams,  etc. 

Water  is  obviously  a  necessity  to  man.    In  the  first  place,  it 


S  WATER   PURIFICATION 

is  used  for  drinking  purposes.     Moreover,  it  is  found  to  be  an 
indispensable  auxiliary  in  almost  every  possible  pursuit. 

Frequently  it  must  be  submitted  to  certain  treatment  before 
use.  The  application  proposed  serves  as  a  method  of  differentia- 
tion. One  can  distinguish,  therefore,  two  processes  :  purification 
of  water  for  drinking  purposes,  and  for  technical  purposes. 

A.    Purification  of  Water  for  Drinking  Purposes. 

Water  used  for  human  consumption  must  be  free  from  sus- 
pended matter.  It  must  be  colourless,  odourless,  agreeable  to  the 
taste,  and  must  not  have  too  high  a  temperature.  It  should  be 
of  such  a  nature  that  it  may  be  partaken  of  with  pleasure. 
Further,  and  of  chief  importance,  it  must  contain  no  disease 
germs. 

vSurface-water  and  ground-water  are  both  used  for  water 
supply.  Ground-water,  taken  from  certain  depths,  is  free  from 
bacteria ;  for,  during  its  passage  through  the  soil,  it  is  freed 
from  germs,  which  remain  attached  to  the  particles  of  sand  in 
the  ground.  Surface-water,  because  it  is  easily  polluted,  is 
always  more  or  less  rich  in  bacteria. 

The  germs  of  contagious  diseases,  typhoid,  diarrhoea,  cholera, 
and  certain  groups  of  the  so-called  ptomaines,  are  the  most 
important  disease  germs  disseminated  through  water  and  claiming 
consideration.  Pus  germs  also  are  found.  It  is  only  in  ^he  rarest 
cases  possible  to  demonstrate  the  existence  of  disease  germs  in 
infected  water,  since  they  only  occasionally  succee^iji-  entering, 
and  also  between  the  date  of  their  reception  by  the  person  and  the 
development  of  the  sickness  a  period  of  time  always  elapses  (e.g. 
with  typhoid,  one  to  three  weeks).  If,  therefore,  developing 
diseases  give  rise  to  an  investigation,  it  is  usually  too  late  to 
trace  the  origin  to  water.  Quite  apart  from  this,  also,  the  proof 
of  the  existence  of  disease  germs  amidst  the  many  other  harmless 
bacteria  is  a  matter  of  considerable  difficulty. 

Proof  of  the  absence  of  disease  germs  is  not  sufficient,  and  is 
no  guarantee  of  the  harmlessness  of  a  water  to  health.  Sanitary 
opinion  is  based,  however,  upon  the  assumption  that  the  strata 
of  earth  at  slight  depths  are  already  free  from  any  such  germs, 
and  that  therefore  a  discovery  of  bacteria  in  water  proves  that 
it  has  come  into  contact  with  the  outside  world,  that  it  has 


PURIFICATION   FOR   DRINKING   PURPOSES  3 

received  surface  influxes.  In  the  dissemination  of  typhoid  and 
other  contagious  diseases,  the  possibility  that  even  secretions  of 
such  men  or  animals  as  harbour  disease  germs  in  themselves 
have  been  admitted  to  the  water  cannot  be  excluded.  The  more 
influxes  of  surface-water,  the  greater  is  the  probability  of  con- 
tamination in  a  ground-water.  From  these  considerations  it 
follows  that  a  river-water  is  much  more  dangerous  than  the  water 
from  a  suitably  situated  reservoir. 

If  a  natural  water  containing  bacteria  be  used  for  drinking 
purposes  it  must  first  be  rendered  innocuous  to  health.  This 
can  be  done  by  methods  of  filtration  or  of  bacteria  destruction. 
But  the  harmfulness  of  a  surface-water  to  health  is  not  its  only 
fault.  Many  surface-waters,  such  as  river- waters,  have  also  the 
disadvantage  of  an  unappetising  odour  and  taste,  or  a  dis- 
agreeable temperature.  Then,  even  the  sanitary  improvement 
of  water  by  the  destruction  of  bacteria  or  by  filtration  will  only 
remove  the  gravest  danger — the  danger  to  health — but  will 
not  make  of  the  inferior  water  a  good  one.  It  must  furthermore 
be  borne  in  mind,  that  when  such  measures  of  purification  are 
demanded,  failure  must  be  expected  either  of  the  plant  itself 
or  failure  due  to  excessive  demands  on  the  available  material,  of 
which  the  best-known  example  is  the  notorious  water-main  in 
the  Ruhr  district.1  As  regards  filtration,  it  must  be  remarked 
that  removal  of  all  the  bacteria  is  not  effected.  Filtration 
only  brings  about  a  reduction  of  the  number  of  germs.  Since, 
however,  for  the  origination  of  a  contagious  disease  a  definite 
amount  of  disease  germs  is  always  necessary,  reduction  of  the 
germs,  if  it  is  at  all  considerable,  signifies  a  considerable  sani- 
tary improvement  in  the  water. 

Ground-water  from  sufficient  depths  is  therefore  superior, 
for  all  the  above-mentioned  reasons,  to  surface-water,  even  if  the 
latter  be  very  carefully  treated.  But  the  former  also  may  be 
doubtful  for  drinking  purposes.  There  are  two  ways  in  which 
disease  germs  may  reach  a  ground-water  and  make  it  unsafe  as  a 
water  supply.  The  first  manner  in  which  it  may  be  polluted, 
and  the  one  coming  into  consideration  in  the  greatest  number  of 
cases,  is  contamination  from  above..  Through  fissures  in  the 

1  This  water-main  drew  water  from  the  River  Ruhr.  During-  the  year  1911  the 
level  of  the  river  sank  so  considerably  that  the  end  of  the  pipe  lay  above  the  sur- 
face and  no  water  could  be  drawn  off. — Translator. 


4  WATER   PURIFICATION 

ground,  through  leaking  wells,  and  through  a  permeated  ground- 
water,  external  streams  may  be  incorporated  without  sufficient 
previous  nitration.  The  second  method  of  pollution  with  disease 
germs  is  through  the  so-called  subterranean  streams  from  strata 
in  the  earth  rendered  contagious  by  human  refuse.  This  method 
of  pollution  has  been  frequently  affirmed  and  disputed.  There 
come  into  consideration  here  filled-up  waste  sewers,  drains, 
depots  for  faeces,  etc.,  which,  owing  to  underground  hollows,  for 
example,  rat-runs  and  the  like,  are  connected  with  wells,  and 
through  which  the  ground- water  flows  into  the  wells.  Even 
without  direct  hollows  or  runs  existing,  a  certain  amount  of  danger 
is  assumed,  owing  to  insufficiency  of  nitration.  If  the  ground- 
water,  in  its  passage  from  the  suspected  area  to  the  place  where 
it  is  drawn,  flows  through  at  least  10  metres  of  ground  free  from 
objectionable  features,  that  is  regarded,  in  general,  as  adequate 
filtration. 

Occasionally  drinking-water  must  be  purified  for  quite  other 
reasons  than  the  hygienic  reasons  previously  discussed.  In  such 
cases  it  is  a  question  of  removing  substances,  including  salts, 
which  give  the  water  an  unappetising  appearance,  or  make  it 
unsuitable  as  a  drinking-water  or  for  domestic  use.  There  may 
be  present  substances  which  impart  to  the  water  a  certain  cor- 
rosive action  on  the  walls  of  the  pipes  through  which  it  is  led 
or  the  vessels  in  which  it  is  stored. 

Methods  of  water  purification  may  be  divided  into  two  classes, 
those  on  a  large  scale,  which  serve  for  central  water  supply,  and 
those  for  the  purification,  of  water  on  a  small  scale,  which  are 
applicable  on  a  journey,  in  housekeeping,  and  in  industry. 

I.    PURIFICATION    OF    WATER    FOR    DRINKING 
PURPOSES  ON  A  LARGE  SCALE. 

The  purification  of  drinking-water  on  a  large  scale,  in  order 
to  obtain  a  healthy  and  unobjectionable  water,  is  effected  either 
by  filtration  or  sterilisation.  In  the  first  case  the  bacteria  are 
mechanically  removed,  in  the  second  case  they  are  killed. 

(i)  Filtration  Processes. 

The  greater  part  of  the  suspended  matter  can  be  removed  in 
settling  reservoirs,  or  by  leading  the  water  through  clarifying 


FILTRATION   PROCESSES  5 

basins  in  which  the  very  small  velocity  of  the  water  enables  the 
greater  part  of  the  suspensions  to  settle  to  the  bottom. 

Sedimentation  basins  for  the  purification  of  drinking-water 
are  constructed  and  managed  according  to  the  same  principles 
as  those  for  the  purification  of  effluent  waters.  On  this  account 
the  question  may  be  relegated  from  here  to  the  chapter  on  the 
conduct  of  sewage  purification. 

The  most  finely  divided  suspensions,  the  bacteria,  are  not 
removed  from  the  water  in  this  way  ;  for  that  purpose  filtration 
is  required. 

(a)  Slow  Sand  Filtration. 

For  the  sand  filtration  of  drinking-water  we  have  to  thank  the 
Englishman  James  Simpson,  who,  in  the  year  1829,  constructed 
the  first  filter  of  this  type.  In  1839  the  London  Water- 
works introduced  the  first  of  such  filters  for  the  purification  of 
drinking-water.  In  the  year  1853  Simpson  sand  filters  were  also 
constructed  in  Berlin,  and  shortly  afterwards  in  many  other 
towns.  The  inventor  only  had  in  view  the  removal  of  suspended 
matter  and  the  clarification  of  the  water  by  means  of  sand 
filtration.  That  it  would  remove  the  bacteria  he  could  not  have 
anticipated,  as  at  that  time  such  micro-organisms  were  still  un- 
known. We  know  to-day,  however,  that  the  main  importance  cf 
sand  filtration  lies  in  the  elimination  of  bacteria. 

In  case  the  water  does  not  contain  too  large  a  quantity  of 
suspended  matter,  a  preliminary  clarification  is  unnecessary, 
and  the  water  flows  immediately  on  to  the  filters. 

The  filters  (see  Fig.  i)  consist  of  large,  generally  rectangular 
surfaces,  surrounded  by  a  wall.  They  are  filled  with  gravel  and 
sand.  At  the  bottom  there  is  a  layer  of  stones  60  to  150  milli- 
metres in  diameter.  Above  this  rests  a  layer  of  gravel  which 
serves  to  support  the  superimposed  sand,  being  coarser  below 
than  above.  The  layers  of  gravel  are  generally  set  down  with  the 
first  about  the  size  of  nuts  (30  to  60  mm.),  then  one  about  the 
size  of  beans  (20  to  30  mm.),  one  the  size  of  peas  (10  to  20  mm.), 
and  a  layer  about  the  size  of  millet  (3  to  5  mm.).  Over  this  there 
rests  the  layer  of  sand  upon  which  the  raw  water  is  placed  to 
a  certain  depth.  The  sand  and  gravel  layers  can  be  set  down 
together  in  varying  amounts.  The  average  height  of  water,  sand, 
and  gravel  is  about  O'6o  metre  (2  feet)  each.  The  filtered  water 


6  WATER   PURIFICATION 

flows  away  underneath,  and  passes  thence  into  the  reservoirs 
for  purified  water.  To  supply  a  town  with  filtered  water  a  large 
number  of  such  sand-filters  are  needed. 

The  plans  of  artificial  sand  filters  must  be  so  arranged  that  each 
individual  filter  can  be  separately  filled,  emptied  and  cleansed, 


FIG.  i.     DIAGRAMMATIC  REPRESENTATION  OF  A  SAND  FILTER. 

and  that  the  purified  water  from  each  filter  can  be  drawn  upon 
independently.  Only  in  this  way  is  complete  control  of  each  sepa- 
rate filter  possible.  The  water  filters  the  more  quickly  through  the 
sand  the  larger  the  size  of  the  grains.  Coarser  sand  does  not  yield, 
however,  such  pure,  germ-free  water  as  does  the  finer  sand.  With 
this  finer  sand  the  surface  of  the  filter  layer  clogs  up  more 
quickly  than  with  the  coarser,  which  latter  is  easier  to  clean. 

Further,  similarity  of  form  in  the  sand  is  important.  The 
more  dissimilar  the  particles  of  sand  are,  the  more  erratically  the 
filter  works.  In  the  cleaning  of  the  filter  the  fine  sand  is  in 
part  washed  away  ;  sand  must  therefore  be  added  from  time 
to  time  to  the  filter,  according  to  the  length  of  time  it 
is  in  use,  if  it  is  not  to  become  continually  coarser.  Whilst 
the  form  of  the  filter  must  be  adapted  to  the  disposition  gi  the 
available  space,  its  size  varies  considerably.  The  size  of  a  filter, 
according  to  Konig,  varies  in  a  series  of  large  towns  from  607  to 
7600  square  metres,  and  is  on  the  average  about  2000  to  3000 
square  metres.  The  water  should  be  maintained  in  the  filters 
as  far  as  possible  at  the  same  height.  The  entry  of  the  water 
to  the  filter  takes  place  continuously  from  above,  and  the  entrance 
of  course  lies  opposite  to  the  discharge-pipe.  Frequently  the 
inflow  of  water  is  automatically  regulated  by  means  of  valves, 
to  bring  about  as  uniform  an  inflow  as  possible.  A  uniform 
discharge  of  water,  also,  is  of  no  less  importance.  In  consequence 
of  the  gradually  increasing  clogging  of  the  filter  the  velocity  of 
discharge  would  always  become  less  if  the  head  of  water  were 


FILTRATION  PROCESSES  7 

not  increased.  This  head  of  water  is  the  difference  of  water-level 
in  the  filter  and  in  the  pure-water  reservoir.  To  increase  the 
head  it  is  best  to  diminish  the  water  pressure  in  the  pure-water 
reservoir,  since,  as  already  mentioned  above,  it  is  not  advan- 
tageous to  alter  the  amount  of  water  in  the  filter. 

In  the  Berlin  Waterworks  the  head  amounts  to  60  or  65 
millimetres,  in  Altona  to  1422  millimetres,  in  Kiel  to  1000  milli- 
metres. 

In  order  to  permit  the  air  enclosed  in  the  filter  to  pass  out, 
so  that  it  is  not  constrained  to  escape  to  the  top,  thus  causing  a 
breaking-up  of  the  filter-bed,  tubes  for  the  removal  of  the  air 
are  let  into  the  side-walls. 

Filters  are  either  covered  or  uncovered,  both  systems  having 
their  advantages  and  disadvantages. 

Open  filters  have  the  disadvantage  that  during  frosty  weather 
cleaning  is  made  very  difficult,  owing  to  the  freezing  of  the  moist 
sand.  This  objection  disappears  with  covered  filters.  On  the 
other  hand,  covered  filters  are  far  more  costly, 

A  further  disadvantage  of  the  covered  filter  is  that  with  it 
the  sediment  layer  is  formed  more  slowly  and  more  imperfectly, 
and  the  covered  filters,  consequently,  do  not  yield  a  sufficiently 
germ-free  water  so  quickly.  This  is  readily  explained,  as  the 
sediment  layer  is  composed  in  part  of  organisms  containing 
chlorophyll,  and  consequently  needing  light,  which  organisms 
cannot  increase,  or  can  only  do  so  more  slowly  than  is  the  case 
with  open  filters  exposed  to  the  full  light. 

In  practice  the  filters  are  arranged  thus.  They  are  filled  with 
water  from  below  to  just  above  the  surface  of  the  sand  ;  then 
the  impure  water  is  allowed  to  flow  in  from  above,  and  to  remain 
at  rest  for  a  period  of  time  during  which  the  formation  of  the 
sediment  layer  is  accelerated.  The  filtrate  is  allowed  to  flow  away 
until  the  germ  content  has  reached  a  certain  limit,  generally  100 
or  less  per  cubic  centimetre  (1600  per  cubic  inch).  Then  the  pipe 
to  the  pure-water  reservoir  is  connected. 

After  a  certain  time,  when  the  sediment  layer  has  become  too 
strong,  the  filter  works  itself  dead,  and  no  more  water  passes 
through.  It  must  then  be  purified.  For  this  purpose  a  layer 
of  sludge,  generally  about  one  inch  thick,  is  first  of  all 
scraped  off.  The  sand  lying  underneath  likewise  contains  a  lot 
of  dirt,  which  is,  however,  of  the  greatest  importance  for  the 


8  WATER   PURIFICATION 

filter  layer  about  to  be  constructed.  After  removal  of  the  layer 
of  sludge,  therefore,  the  sand  is  loosened  to  a  depth  of  about 
8  inches,  and  the  filter  is  then  allowed  to  remain  unused 
for  a  day,  to  permit  the  access  of  fresh  air.  The  so-called 
journey  (running  time)  of  a  filter  is  likewise  very  varied.  From 
eleven  different  waterworks,  according  to  Konig,  it  amounts  on  an 
average  to  25-5  days,  during  which  the  amount  of  water  filtered 
per  square  metre  averaged  69-3  cubic  metres. 

From  time  to  time  the  sand  must  also  be  replaced  by  fresh  or 
washed  sand.  It  is  removed  down  to  the  layer  of  gravel,  new 
sand  filled  in,  and  this  is  covered  with  a  layer  of  the  lower  portion 
of  used  sand,  which  has  a  sticky  nature  and  accelerates  the 
formation  of  the  sediment  layer.  Washed  sand  is  only  to  be 
recommended  in  place  of  fresh  sand  in  cases  where  the  fresh 
material  is  dearer  than  the  washed,  since  by  washing  more  or  less 
of  the  fine  useful  portion  of  the  sand  is  removed.  For  this 
reason  a  sand  which  has  been  washed  many  times  must  be 
replaced  by  fresh  sand.  The  washing  of  the  sand  takes  place 
automatically  in  drums,  or  boxes,  in  which  the  sand  comes  many 
times  into  contact  with  fresh  water.  There  are  numerous  different 
systems  of  sand  washing. 

The  more  slowly  filtration  takes  place,  the  purer,  as  a  general 
rule,  is  the  filtrate.  The  velocity  of  filtration,  which  varies  largely 
in  different  waterworks,  amounts  on  an  average  to  about  100 
millimetres  (4  inches)  per  hour. 

Very  soon  after  the  introduction  of  sand  filtration  it  was 
recognised  that  the  sediment  layer  would  be  difficult  to  control. 
This  layer  consists  for  the  most  part  of  organic  suspended  matter, 
displaying  either  living  organisms  or  dead  substances,  while 
there  is  also  present,  in  smaller  degree,  inorganic  matter  like  clay, 
oxide  of  iron,  etc.  The  most  varied  organisms  are  to  be  found 
in  the  composition  of  a  sediment  layer. 

C.  Piefke  demands  a  maximum  filtration  velocity  of  100  milli- 
metres per  hour,  while  other  investigators  could  establish  no 
variation  in  the  bacteriological  and  chemical  composition  of  the 
water  with  considerably  greater  velocities. 

C.  Piefke  found,  further,  that  with  an  increase  in  the  pressure 
of  filtration  the  bacteria  content  of  the  pure  water  rises,  more 
so,  of  course,  the  more  bacteria  the  raw  water  contains.  He 
also  proved  by  investigation  that  a  filter  freed  from  the 


FILTRATION   PROCESSES  9 

sediment  layer  yields  water  of  small  bacteria  content  more 
quickly  than  fresh  sand.  This  is  explained  by  assuming  that  the 
suspended  matter  penetrates  into  the  sand  a  little,  and  this  sand 
layer,  containing  suspended  matter,  takes  part  in  the  work  of 
nitration.  Of  great  importance  is  the  answer  to  the  question, 
whether  the  bacteria  in  the  pure  water  have  passed  through  the 
filter  during  the  filtration  of  the  raw  water,  and  therefore  are 
derived  from  the  raw  water,  or  whether  they  are  washed  away 
from  the  sediment  layer  or  from  the  sand.  By  their  investiga- 
tions on  this  question,  Frankel  and  Piefke  came  to  the  con- 
clusion that  the  quantity  of  micro-organisms  passing  over  into 
the  filtrate  is  proportional  to  the  bacteria  content  of  the  raw 
water. 

For  towns  which  have  to  deal  with  very  poor  raw  water,  like 
Hamburg,  Altona,  Konigsberg,  Warsaw,  and  others,  double 
filtration,  proposed  by  Gotze,  is  to  be  recommended.  The 
most  diverse  hygienists  express  themselves  very  approvingly 
concerning  this  method.  By  double  filtration,  the  raw  water 
already  passed  once  through  a  sand  filter  is  sent  again  through  a 
filter  well  clogged  with  sludge.  Gotze  showed  that  with  double 
filtration  a  raw  water  with  a  germ  content  of  28,000  was  purified 
to  one  of  780  bacteria  per  cubic  centimetre  in  the  preliminary 
filtration,  and  to  31  per  cubic  centimetre  in  the  final  filtrate. 
The  preliminary  filtration  of  Puech-Chabal  is  largely  employed. 
In  this  system  the  water  is  purified  by  a  series  of  coarse  prelimin- 
ary filters.  The  fine  filter  then  employed  has  only  to  further 
diminish  the  already  considerably  reduced  quantity  of  bacteria, 
so  that  the  water  can  be  regarded  as  free,  bacteriologically,  from 
objection. 

The  cost  of  sand  filtration,  exclusive  of  interest  and  repayment 
of  loans,  amounts  on  an  average  to  o-7d.  to  2'5d.  per  1000 
gallons  (Konig). 

The  filtered  water  is  submitted  to  a  continuous  bacteriological 
control.  The  constant  estimation  of  the  number  of  bacteria 
is  an  excellent  means  of  settling  whether  the  filter  is  working 
well.  A  crack  arising  in  the  sand,  or  any  other  abnormality, 
reveals  itself  immediately  in  a  rise  of  the  number  of  bacteria. 
The  official  rule  runs  that  pure  water  should  not  contain  above 
100  germs  per  cubic  centimetre. 


10  WATER   PURIFICATION 

(b)  Percolating  or  Dry  Sand  Filters. 

In  France,  recently,  the  so-called  percolating  sand  filters  have 
come  into  use  for  water  purification.  They  are  based  on  the 
theory  that  oxygen  plays  a  part  in  the  removal  of  bacteria, 
especially  of  the  pathogenic  kind.  The  ordinary  filter  can  contain 
no  oxygen,  since  it  is  always  covered  by  water.  On  this  account 
the  percolating  sand  filter  is  employed  similarly  to  the  per- 
colating filters  in  bacterial  sewage  purification,  except  that  it  is 
composed  of  fine  material  (sand). 

Miquel  and  Mouchet,  in  laboratory  investigations,  were  unable, 
after  using  this  method,  to  prove  the  presence  of  typhoid  bacilli 
added  to  the  raw  water. 

This  method  was  tested  by  Baudet,  in  Chateaudun  (France), 
working  on  a  large  scale.  The  results  seem  very  favourable. 
The  number  of  bacteria  fell  from  between  293  and  1498  in  raw 
water,  to  6  bacteria  per  cubic  centimetre  in  pure  water.  Espe- 
cially remarkable  is  the  consideration  that  in  the  pure  water 
bacterium  coli  was  never  found. 

This  filter  likewise  requires  several  months  to  build  up,  and 
the  velocity  of  filtration  cannot  be  raised  indefinitely ;  still,  the 
percolating  sand  filters  seem  to  be  considerably  more  pro- 
ductive than  the  slow  sand  filter. 

Baudet  maintains  that  with  a  clear  but  bacteriologically  impure 
water,  results  are  obtained  with  percolating  sand  filters  which  are 
better  and  less  troublesome  than  those  obtained  by  any  other 
method. 

The  introduction  of  the  filter  for  barracks  has  been  recom- 
mended by  the  French  Army  administration.  In  Germany  the 
filters  have  not  yet,  to  my  knowledge,  come  into  use.  Further, 
there  has  been,  up  to  the  present,  no  German  investigation  of 
the  method. 

(c)  Mechanical  Filters. 

The  considerable  cost  of  sand  filters  in  relation  to  their  pro- 
ductivity, and  the  great  space  necessary  for  a  sand-filter  installa- 
tion, shows  clearly  the  advisability  of  replacing  the  sand  filter 
in  technical  work  by  other  apparatus  which  takes  up  less  room 
and  permits  a  greater  velocity  of  filtration.  From  these  considera- 
tions the  mechanical  filter  originated.  Since  the  natural,  workable 
layer  is  first  formed  after  a  long  interval  of  filtration,  chemicals 


FILTRATION   PROCESSES  11 

are  generally  added  to  the  water,  especially  with  the  newer  filters 
of  this  type,  in  order  to  produce  an  artificial  plankton  and  an 
artificial  filter  layer.  With  the  mechanical  filters  of  newer 
pattern,  aluminium  sulphate  is  almost  always  used  for  this 
purpose,  as  it  reacts  with  the  alkaline  earths  present  in  the  water 
according  to  the  following  equation  : 


Most  of  the  flocculent,  gelatinous  aluminium  hydroxide  sinks 
to  the  bottom,  and  the  suspended  matter  travels  along  with  it. 
The  flakes  still  remaining  in  the  water  form  a  sediment  layer  on 
the  filter.  The  velocity  of  filtration  exceeds  that  of  the  sand 
filter,  generally  being  60  or  70  times  more  rapid. 

There  is  a  large  number  of  different  systems  of  the  mechanical- 
filter  type. 

Older  patterns  are,  for  example,  the  Anderson  revolving 
purifier,  the  Warren  Filter,  the  Krohnke  Filter. 

Filters  of  newer  construction  are,  amongst  others,  the  Jewell 
Export  Mechanical  Filter,  the  Halvor  Breda  Filter,  the  Bell 
Filter,  Reeves  Filter,  Candy  Filter,  Puech  Filter,  Sucro  Filter. 

These  filters  are  not  only  employed  for  removing  bacteria  from 
drinking-water,  they  frequently  find  application  in  technical  work. 

As  a  type  of  this  filter  the  Jewell  Export  Filter,  which  has  been 
studied  closely  from  different  points  of  view,  may  be  described 
more  carefully. 

The  Jewell  Export  Mechanical  Filter.  —  The  Jewell  Filter,  repre- 
sented in  Figure  2,  consists  of  the  steel  cylinder  containing  the 
filter-bed,  which  is  encased  in  a  second  cylinder  of  somewhat 
larger  diameter,  so  that  between  the  two  there  is  an  annular  space 
which  is  closed  underneath.  In  this  annular  space,  through  the 
valve  situated  on  the  left-hand  side,  the  raw  water,  which  has 
been  previously  treated  in  sedimentation  tanks,  and  also  with 
aluminium  sulphate,  passes  into  the  filter,  in  order  to  flow  over 
the  edge  of  the  inner  cylinder  on  to  the  filter-bed.  After  it  has 
streamed  through  the  filter-bed,  composed  of  sand,  it  passes  at 
the  bottom  through  sieve  heads  in  a  system  of  outlet  tubes  which, 
in  their  turn,  fit  into  a  diametrically  placed  collector,  and  to 
which  they  are  all  rectangularly  placed.  From  the  collector 
the  water  passes  through  the  regulator  (Weston  Controller), 
shown  in  the  front  of  the  diagram  on  the  right  side,  into  the 


12  .  WATER   PURIFICATION 

pure- water  basin  to  be  found  underneath.  This  regulator  serves 
to  keep  filtration  constant.  The  importance  of  a  constant 
velocity  of  filtration  has  already  been  brought  into  prominence 
in  the  case  of  sand  filters.  With  mechanical  filters  this  importance 
is  increased  owing  to  the  employment  of  chemical  coagulants 
associated  with  it,  and  which  can  only  be  added  in  these  cases 
in  precisely  estimated  amounts.  By  means  of  a  float  working  on 
a  throttle-valve  (shown  on  the  left  in  the  diagram)  the  inflow  is 


FIG.  2.     THE  JEWELL  EXPORT  MECHANICAL  FILTER. 


also  regulated,  and  the  water  in  the  filter  kept  at  a  constant 
height. 

To  clean  the  filter  the  water  takes  the  reverse  direction.  It 
is  allowed  to  stream  in  under  the  pressure  of  a  pump  or  a  high 
reservoir,  through  the  cleaning-valve  situated  at  the  extreme 
right  in  the  diagram.  It  is  then  allowed  to  flow  through  the 
collector,  exit  tubes,  and  filter-bed  in  the  reverse  direction  from 
bottom  to  top,  to  pass  over  the  rim  of  the  inner  cylinder  into  the 
annular  space,  out  of  which  it  streams  into  the  effluent  tube, 
through  a  valve  not  visible  in  the  diagram.  At  the  same  time  the 
stirring  arrangement  shown  in  the  diagram  is  set  in  motion,  which 
thereby  gets  the  whole  of  the  filter-bed  into  a  floating  condition, 
so  that  each  separate  particle  of  sand  is  washed  by  the  water 


FILTRATION   PROCESSES  13 

and  is  consequently  thoroughly  purified.  In  the  cleaning  process 
it  is  necessary,  of  course,  that  the  cleansing  water  be  distributed 
uniformly  over  the  whole  surface  of  the  filter-bed,  so  that  no 
stagnant  corners  or  angles  result.  This  important  need  is  met 
in  the  Jewell  Filter  by  keeping  the  throats  of  the  strainers  in  the 
outlet  tubes  very  narrow,  so  that  the  pressure  and  velocity  of  the 
cleansing  water  at  these  points  are  very  large. 

After  the  first  cleaning  there  comes  a  further  cleansing  process, 
in  which  the  first  water  filtered  is  allowed  to  flow  through  the 
third  of  the  three  valves  shown  on  the  right  of  the  diagram,  in 
order  to  remove  the  muddy  water  still  present  in  the  filter.  The 
cleaning  and  the  subsequent  operation  take  up  about  ten  minutes, 
and  are  effected  as  a  rule  once  daily.  The  starting  of  the  filter 
is  always  performed  mechanically  without  any  manual  labour 
on  the  filter-bed. 

Jewell  Filters  have  come  into  use  largely  for  the  water  supply 
of  municipalities.  I  mention  the  towns  of  Alexandria,  Trieste, 
Helsingfors  (Finland),  Annecy  (France).  Critical  examinations 
on  the  basis  of  the  tests  previously  put  forward  generally  prove 
favourable. 

Bitter  and  Gottschlich  have  obtained  very  favourable  results 
with  the  Jewell  Export  Filter  in  Alexandria. 

Hilgermann  has  likewise  made  investigations  with  the  Jewell 
Export  Filter,  and  come  to  fewer  favourable  results.  He  holds, 
according  to  his  experiments,  that  the  Jewell  Export  Filter,  like 
every  other  mechanical  filter,  is,  in  bacteriological  respects, 
absolutely  inferior  to  the  sand  filter. 

K.  Schreiber  has  searchingly  investigated  the  Jewell  Filter, 
in  a  series  of  experiments  with  an  experimental  plant  at  the 
Berlin  Waterworks,  and  comes  to  the  conclusion  that  it  is  quite 
as  good  as  the  sand  filter  in  bacteriological  respects,  in  the 
removal  of  the  turbidity  and  colour  of  the  raw  water,  as  well 
as  in  the  method  of  washing,  which  takes  place  quite  mechani- 
cally, without  danger  of  contamination  from  the  hands  and 
clothes  of  the  workmen.  According  to  Schreiber,  the  method 
may,  however,  be  far  superior  to  the  sand-filtration  method. 

The  amount  of  aluminium  sulphate  added  is  of  great  import- 
ance. Schreiber  comes  to  the  conclusion  that  with  an  addition 
°f  33*6  g.  of  aluminium  sulphate  per  cubic  metre  (5  oz.  per  1000 
gallons),  with  a  time  of  sedimentation  lasting  i  hour  28  minutes, 


14  WATER   PURIFICATION 

and  at  a  velocity  of  filtration  of  4  metres  (13  feet)  per  hour, 
94-3  per  cent  of  the  bacteria  in  the  raw  water  are  removed  by  the 
Jewell  Export  Filter. 

The  increase  of  sulphates  occasioned  by  the  addition  of  the 
chemicals  is  confined  within  such  narrow  limits  that  a  deteriora- 
tion of  the  water  for  drinking  and  domestic  purposes  does  not 
come  into  the  question  in  practice. 

The  increase  of  aluminium  salts,  apart  from  the  consideration 
that  this  disappears  completely  with  well-ordered  management, 
is  so  small  that  hygienically  it  may  be  neglected.  At  all  times  in 
those  places  where  in  the  water-supply  plant  there  is  no  horizontal 
space  at  disposal  for  expansion,  the  Jewell  Export  Filter  can  be 
applied  with  advantage,  as,  for  example,  in  cases  of  water  supply 
in  besieged  strongholds  in  time  of  war. 

Further,  Friedberger  has  also  carried  out  searching  investiga- 
tions with  the  Jewell  Filter,  with  the  water  of  the  town  of  Konigs- 
berg.  He  comes  to  fewer  favourable  conclusions  than  Schreiber. 
With  water  rich  in  bacteria,  mechanical  filtration  does  not 
guarantee  so  complete  a  reduction  of  the  bacteria  that  one  could 
be  satisfied  with  mechanical  filtration  alone. 

A  quite  new  work  of  Gottschlich  and  Bitter  gives  an  account 
of  over  four  years'  practical  experience  of  Jewell  Filter  man- 
agement for  the  town  of  Alexandria.  The  plant  worked 
excellently  during  this  time  as  regards  removal  of  bacteria  and 
turbidity,  as  well  as  the  trustworthiness  of  the  method. 

(d)  Artificial  recovery  of  Ground-water  from  Surface-water 
(Intermittent  filtration) . 

For  the  reasons  discussed  on  page  2  ground-water  is  to  be  pre- 
ferred to  purified  surface-water.  As  a  consequence,  municipalities 
which  are  in  a  position  to  do  so  are  always  attempting  to  supply 
themselves  more  and  more  with  ground-water  for  drinking 
purposes.  In  order  to  obtain  such  water  in  sufficient  quantity, 
many  towns  find  it  necessary  to  go  a  considerable  distance  from 
the  town.  Considerable  expense  thereby  results  in  conveying, 
and  also  in  superintending  the  water  conduits,  etc.  Owing  to  the 
expense  of  bringing  water  from  a  distance,  it  has  been  attempted 
many  times  to  increase  artificially  the  ground-water  in  the 
neighbourhood  of  towns. 


FILTRATION   PROCESSES  15 

The  recovery  of  artificial  ground-water  was  originated  scienti- 
fically by  Thiem. 

So-called  natural  sand  or  bank  filtration  comes  into  considera- 
tion here.  It  consists  in  the  sinking  of  wells  on  the  banks  of  a 
lake  or  river.  The  water  in  these  wells  is  then  pumped  away,  and 
its  level  thereby  considerably  lowered.  As  a  consequence  water 
enters  the  wells  from  the  lake  or  the  river  through  the  sand  or 
gravel  strata,  which  act  as  the  filtering  medium. 

In  its  progress  through  the  ground  the  water  is  freed  from 
bacteria  in  a  manner  similar  to  ground-water.  Bank  filtration 
results  in  the  suspended  matter  being  gradually  drawn  through 
the  sand.  As  opposed  to  artificial  sand  filtration  in  which  fil- 
tration is  vertical,  bank  filtration  is  horizontal,  and  this  is  really 
the  cause  of  the  observed  passage  of  suspended  matter  through 
the  filtering  layer. 

The  investigations  of  Scheelhaase  with  Maine  River  water 
showed  that  with  wells  at  a  distance  of  25  metres  from  the  river- 
bank,  while  the  bacteria  were  of  course  removed,  the  water  had 
become  like  ground-water  in  no  other  respects,  since  the  tempera- 
ture was  not  sufficiently  adjusted,  nor  was  its  odour  nor  taste 
improved. 

Intermittent  filtration  in  a  vertical  direction  has  later  been 
investigated  in  various  ways.  According  to  Richert  there  are 
the  following  methods  :  The  surface-water  is  conducted  to  an 
irrigation  field,  where  it  is  allowed  to  drain  away.  This  method 
ought  to  have  been  tested  on  an  experimental  scale.  It  has  proved 
of  little  use,  as  it  is  untrustworthy  and  difficult  to  control. 

It  is  better  to  lead  the  surface-water  to  an  intermittent  filtra- 
tion basin  or  well,  which  has  been  sunk  to  the  ground-water  level, 
or  to  a  basin  which  lies  over  the  ground-water. 

Success  in  producing  a  workable  ground-water  depends  on  the 
possibility  of  leading  the  stream  sufficiently  far  in  a  horizontal 
direction,  and  on  the  water  having  time,  apart  from  the  removal 
of  bacteria,  to  become  a  useful  ground-water  in  respect  of  the 
temperature,  colour,  taste,  and  smell.  In  this  direction,  Scheel- 
haase, in  Frankfort-on-Maine,  has  lately  published  important  and 
interesting  researches. 

River  Maine  water  purified  by  means  of  a  sand  filter  was  allowed 
to  flow  to  a  double-branch  irrigation  bed  laid  out  3  metres  deep, 
50  metres  long,  and  constructed  of  gravel  and  drans.  The 


16  WATER   PURIFICATION 

infiltrate,  finely  distributed  by  this  treatment,  had  to  trickle 
in  a  vertical  direction,  to  the  natural  ground-water  level,  through 
a  layer  of  ground  13  to  14  metres  deep,  consisting  of  fine  sand 
and  gravel.  Then  it  joined  with  the  natural  ground-water,  and 
flowed  along  with  it  to  the  nearest  pumping-station  following 
the  incline  of  the  ground.  The  result  of  the  investigation  was  that 
at  100  metres  from  the  place  irrigated,  a  distance  which  the  in- 
filtrate flowed  through  in  190  days,  Maine  water,  which  is  very 
dirty  river-water,  had  been  transformed  as  regards  its  bacterio- 
logical nature,  its  temperature,  smell,  taste,  and  colour,  into  a 
water  equally  as  good  as  ground-water. 

J.  Braikowitz  reports  on  the  nature  of  artificial  ground- water 
in  different  towns  :  "  In  Offenbach-on-Maine  the  water  of  the  old 
waterworks  is  brought  to  the  neighbourhood  of  the  new  works, 
which  draws  upon  a  well  of  water  free  from  any  objection.  In 
Brunswick  the  condenser  water  from  steam  engines  in  the  water- 
works is  made  to  percolate  through  the  ground,  whereby  the 
ground-water  obtained  only  experiences  a  rise  in  temperature 
of  0-4°  C.  In  the  Ruhr  Waterworks  the  river- water  is  led  through 
ditches,  or  through  a  broken-up  portion  of  the  choked-up  river-bed, 
to  the  layer  of  rubble-stone  underneath.  The  Ruhrtalsperren  Co. 
seeks  to  increase  the  lower  waters  of  the  Ruhr,  and  also  to 
augment  the  ground-water,  by  constructing  dams." 

According  to  Richert  the  ground-waterworks  of  the  town  of 
Schweinfurt  is  a  beautiful  example  of  natural  filtration. 

Since  the  year  1875  the  town  of  Chemnitz  has  employed  inter- 
mittent filtration  with  the  best  results,  in  which,  above  a  series 
of  wells  sunk  in  a  ground-water  area,  an  irrigation  field  for 
intermittent  filtration  was  dug  out  to  the  ground-water  level. 
The  water  introduced  into  the  open  ditches  of  the  irrigation  field 
unites  directly  with  the  ground-water,  and  flows  along  with  it  to 
the  wells. 

In  a  similar  manner  the  town  of  Gothenburg  produces  artificial 
ground-water. 

(e)  The  Importance  of  Water  Filtration  in  Public  Health  Ad- 
ministration, and  Critical  Opinions  on  the  value  of  Sand 
and  Mechanical  Filtration. 

The  purification  of  surface-water  for  drinking  purposes  by 
means  of  filtration  has  become  a  question  of  great  importance 


FILTRATION   PROCESSES  17 

as  affecting  the  health  of  towns  and  their  economic  improve- 
ment. 

According  to  Hilgermann,  cholera  and  typhoid  diseases 
especially  have  decreased  in  those  places  where  sand  filtration 
has  been  introduced  and  properly  conducted.  In  those  places 
where  epidemics  have  appeared  in  spite  of  nitration,  they  have 
been  caused  by  faulty  arrangement  of  the  sand  filter  or  faulty 
management  of  the  undertaking.  During  the  cholera  epidemic 
in  Hamburg,  in  the  year  1892,  sand  filtration  worked  splendidly, 
since,  for  example,  the  town  of  Altona,  which  used  filtered  Elbe 
water,  was  quite  free  from  the  epidemic  although  the  filters 
received  for  their  work  Elbe  water,  rendered  contagious  by  all 
the  Hamburg  discharges. 

According  to  Vincey,  as  recently  as  1905  a  number  of  town- 
ships around  Paris  employed  raw  Seine  water.  After  the  intro- 
duction of  sand  filters  mortality  in  typhoid  cases  fell  about 
42  per  cent,  cases  of  typhoid  about  48  per  cent. 

Hilgermann,  in  his  work  already  mentioned,  critically  com- 
pared the  newer  American  mechanical  filters  with  the  sand 
filter. 

European  workers  who  have  experimented  in  recent  years 
with  American  mechanical  filters  have  in  general  come  to  favour- 
able conclusions.  American  professional  men  who  have  had  the 
opportunity  of  studying  the  mechanical  filter  on  the  spot  for 
ten  years  are  not  especially  favourable. 

According  to  Hilgermann,  the  main  difficulty  with  the  American 
mechanical  filters  which  work  by  addition  of  aluminium  sulphate, 
is  that  it  is  not  possible,  with  the  varying  composition  of  the  raw 
water,  to  add  the  right  amount  of  chemicals.  This  causes  faulty 
sedimentation  and  faulty  formation  of  the  filter  layer. 

On  the  basis  of  his  researches  with  the  Jewell  Filter,  Hilger- 
mann comes  to  the  following  conclusions  on  the  working  of  the 
mechanical  filter  : — 

1.  With  raw  water  containing  a  small  number  of  bacteria 
the  American  mechanical  filter  yields  good  results. 

2.  The  efficiency  of  the  whole  method  of  filtration  depends 
upon  the  sedimentation. 

3.  The  addition  of  aluminium  sulphate  at  any  time  is  dependent 
upon  the  amount  of  the  substances  suspended  in  the  raw  water. 

4.  With  poor  raw  water  the  mechanical  filter  fails  if  the  addition 


18  WATER   PURIFICATION 

of  chemicals  cannot  be  immediately  increased  with  the  increase 
of  suspended  matter  in  the  raw  water. 

5.  There  is  no  principle  for  such  a  regulation.     The  increase 
must  be  settled  by  experiment. 

6.  As  regards  the  removal  of  turbidity  due  to  clay  and  also 
the  removal  of  colour,  and  in  respect  of  the  hygienic  method  of 
cleaning,  the  mechanical  filter  is  superior  to  the  sand  filter. 

Closer  examination  shows  that  as  regards  cost,  sand  and 
mechanical  filtration  are  approximately  alike.  Of  course,  the 
cost  of  setting  up  the  mechanical  filter  a  second  time  is  far  smaller 
than  with  the  sand  filter,  owing  to  its  small  dimensions  and  to 
the  small  space  it  requires.  Still,  the  wear  and  tear  of  these 
machines  is  much  greater  than  is  the  case  with  sand  filters  ; 
hence  one  has  to  allow  for  a  greater  depreciation.  Further,  the 
constant  consumption  of  chemicals  raises  the  cost  of  manage- 
ment considerably. 

(ii)   Methods  of  Water  Sterilisation. 

The  removal  of  bacteria  from  water  can  take  place  by  filtration 
and  by  sterilisation,  i.e.  the  destruction  of  the  bacteria.  For 
this  purpose  a  number  of  chemicals  have  been  employed,  e.g. 
ferric  chloride,  chrome  iron  alum,  lime,  hydrogen  peroxide, 
calcium  permanganate,  chloride  of  lime,  bromine,  copper 
chloride,  organic  acids,  ozone,  etc.  Of  these  very  many  must  be 
rejected,  since  they  either  do  not  work  with  certainty  in  general, 
or  they  need  a  long  time  for  the  development  of  their  sterilising 
action,  or  they  alter  the  appearance,  smell,  and  taste  of  the  water 
too  much.  The  only  methods  of  any  practical  value  are  those  in 
which  ozone  and  chlorine  (as  chloride  of  lime  or  sodium  hypo- 
chlorite)  are  used. 

(a)  The  Ozone  Method. 

Ozone,  the  so-called  active  oxygen,  which  is  formed  from  the 
oxygen  of  the  air  by  the  silent  discharge  of  high-tension  electric 
current,  has  proved  to  be  a  good  medium  for  sterilising  water. 
When  dissolved  in  water  it  kills  the  greater  part  of  the  bacteria 
and  then  escapes  again  from  the  water,  without  influencing 
taste  or  smell  in  the  slightest  degree,  since  it  decomposes  to 
ordinary  oxygen.  For  the  sterilisation  of  drinking-water  a  number 
of  ozone  plants  of  varying  design  have  been  proposed ;  for  example, 


20  WATER   PURIFICATION 

the  system  of  Siemens  and  Halske,1  Trindall,  Abraham  Marmier, 
Otto  and  Vosmaer.  Quite  a  number  of  towns  now  purify  their 
water  by  means  of  ozone,  e.g.  Paderborn-i.-W.,  St.  Petersburg, 
Hermannstadt,  Nizza,  St.  Mans,  near  Paris,  and  others. 

As  an  example  of  an  ozone  plant,  that  of  the  metropolis,  St. 
Petersburg,  may  be  more  closely  described  here  as  one  of  the 
newest  according  to  the  system  of  Siemens  and  Halske.  As 
can  be  seen  from  Figure  3,  the  raw  water  is  taken  direct  from  the 


FIG.  4.     OZONE  WATERWORKS  OF  ST.  PETERSBURG. 

Neva  by  means  of  a  pump,  and  pumped  to  the  sedimentation 
reservoirs  for  purification.  Before  entering  the  purification 
reservoir  the  water  is  treated  with  aluminium  sulphate.  It  is 
then  filtered  through  thirty-eight  mechanical  filters.  These  filters 
are  on  the  Howatson  system,  which  is  similar  in  many  respects 
to  the  previously  described  Jewell  Filter.  To  the  filtration  plant 

1  Recently  the  Berlin  Ozone  Company  has  incorporated  the  firms  of  Siemens 
and  Halske  and  the  General  Electric  Co.,  and  has  taken  over  all  the  patents 
of  Siemens  and  Halske. 


STERILISATION   PROCESSES  21 

there  is  attached  the  actual  ozone  plant,  which  consists  of  two 
parts,  the  ozone  batteries  and  the  steriliser. 

In  Figure  4,  on  the  left,  the  ozone  batteries,  consisting  of  128 
pieces  of  apparatus,  are  shown,  and  on  the  right  the  five  sterilisers 
can  be  seen,  one  of  which  serves  as  a  reserve.  The  individual 
apparatus  are  Siemens  and  Halske  ozone  cylinder  elements,  as 
shown  in  Figure  5.  In  this  apparatus  the  oxygen  of  the  air  is 
converted  into  ozone  by  means  of  high-tension  discharges.  The 


llffl 


FIG.  5.     OZONE  WATERWORKS,  ST.  PETERSBURG.     OZONE  BATTERIES. 

concentration  of  ozone  amounts  to  2-5  grams  in  i  cubic  metre 
(i  grain  per  cubic  foot)  of  ozonised  air.  The  air,  before  entering 
the  apparatus,  is  dried  in  a  cooling  machine.  The  movement  of 
the  air  through  the  ozone  batteries  and  pipes  takes  place  by  the 
aid  of  the  so-called  emulsifiers  (Otto's  system).  These  emulsifiers 
are  injectors  or  water- jet  air-pumps,  which,  by  means  of  a  water 
pressure  of  about  4  metres  (160  in.),  sucks  the  ozonised  air  out 
of  the  ozone  batteries,  and  brings  it  mixed  with  water  into  the 
steriliser.  The  absorption  of  the  ozone  and  the  consequent  steri- 
lisation of  the  water  takes  place  partly  in  the  emulsifiers  placed 


22  WATER   PURIFICATION 

near  the  sterilisers,  and  partly  in  the  agitators,  from  the  bottom  of 
which  the  ozonised  air  rises  to  the  top  in  a  very  fine  state  of  divi- 
sion, and  therefore  in  very  intimate  contact  with  the  water.  From 
the  emulsifiers  and  sterilisers  the  water  passes  over  a  cascade  for 
removing  the  air  to  a  pipe  which  leads  it  to  the  pure-water  reser- 
voir. From  there  it  is  pumped  away  into  the  town's  mains. 

It  is  a  necessary  preliminary  for  the  satisfactory  working  of  an 
ozone  plant  that  the  water  to  be  sterilised  contain  no  suspended 
matter,  and  not  too  large  an  amount  of  organic  matter,  or  ferrous 
oxide.  In  such  cases  the  ozone  is  in  great  part  consumed  in  the 
oxidation  of  the  dissolved  substances,  or  of  the  iron.  The 
unsatisfactory  working  of  a  plant  in  Schierstein  was  attributed 
to  the  presence  of  a  considerable  amount  of  iron  in  the  drinking- 
water. 

The  researches  undertaken  by  Erlwein,  Ohlmuller,  and  Prall  on 
the  "Auftrage  des  Kaiserlichen  Gesundheitsamtes"  (Commission 
of  the  Imperial  Sanitary  Board),  and  by  Proskauer  and  Schuder,of 
the  "Konigl.  Institut  fur  Inf ektionskrankheiten  "  (Royal  Institute 
for  Infectious  Diseases),  with  the  water  of  the  Spree,  and  with 
water  to  which  large  quantities  of  pathogenic  bacteria  (typhoid, 
diarrhoea,  cholera)  had  been  added,  are  in  agreement  in  proving 
that  the  bacteria  are  almost  entirely  destroyed,  and  that  the 
pathogenic  variety  were  in  all  cases  destroyed  without  exception. 

The  Pasteur  Institute  also  obtained  favourable  results  in  its 
investigations  on  ozone  processes. 

Halbertsma  and  Dolezalek  prove  that  the  opinion  that  no  daily 
control  is  necessary  in  ozone  processes  as  contrasted  with  sand 
filtration  is  wrong. 

Karl  Schreiber,  in  the  "  Auftrage  der  Konigl.  Prufungsanstalt 
fur  Wasserversorgung  und  Abwasserbeseitigung  "  (Commission 
of  the  Royal  Test-Institution  for  Water  supply  and  Sewage 
disposal),  as  a  consequence  of  the  unfavourable  observations  of 
Halbertsma  and  Dolezalek,  undertook  a  searching  examination 
of  the  ozone  works  in  Paderborn,  in  which  he  established  that  the 
ozone  process  satisfied  all  demands. 

G.  W.  Chlopin  and  K.  E.  Dobrowolski  report  that  in  St.  Peters- 
burg the  bacteria  are  not  completely  killed  off,  but  are  decreased 
on  an  average  about  98-8  per  cent.  Intestinal  bacteria  should 
be  absolutely  destroyed.  The  water  should  also  undergo  an 
improvement  in  taste  and  colour.  The  chemical  composition 


STERILISATION   PROCESSES  23 

does  not  alter  essentially,  and  the  ozone  dissolved  in  the  water 
disappears  after  ten  minutes. 

S.  Rideal  reports  on  his  experience  in  the  works  at  Paris. 
After  ozonisation  all  bacteria,  except  the  more  resistible  spores, 
were  destroyed.  The  temperature  of  the  water  was  not  raised. 

According  to  Gartner  the  bacteriological  action  is  as  good  with 
ozonisation  as  with  sand  filtration,  and  it  is  also  more  certain. 

Sauna  made  experiments  in  which  ozone  was  used  in  quantities 
averaging  about  4  milligrams  per  litre  (1.75  grains  per  cubic 
foot.  It  gave  the  following  results :  Nitric  acid  is  completely 
destroyed  ;  15  to  43  per  cent  of  organic  matter  is  oxidised. 
The  efficiency  of  ozone  on  the  organic  matter  increases  accord- 
ing as  the  water  is  more  oxidisable.  Ozone  also  oxidises 
ammonia  present  in  water.  Sulphates,  carbonates,  and  chlorides 
are  not  altered.  Nitrates  and  free  oxygen  show  an  increase. 
Within  a  few  minutes  the  last  traces  of  ozone  disappear. 
Hydrogen  peroxide  is  not  formed  By  using  suitable  amounts  of 
ozone,  complete  sterilisation  of  the  water  takes  place.  Ozone 
acts  most  effectively  on  pathogenic  bacteria. 

The  sterilising  effect  of  ozone  depends,  according  to  Schreiber, 
on  four  factors,  viz. — 

1.  On  the  nature  of  the  water. 

2.  On  the  amount  of  water  passing  through  the  plant. 

3.  On  the  concentration  of  the  ozonised  air. 

4.  On  the  amount  of  the  ozonised  air  used. 

For  the  right  working  and  control  of  ozone  plants,  Schreiber 
recommends  that  a  hygienist  and  an  official  experienced  in 
electrical  management  should  undertake  a  test  of  the  four  factors 
mentioned,  and  that  they  should  then  work  out  regulations  for 
running  the  process  in  accordance  with  the  test.  The  finished 
plan  should  be  tested,  as  regards  its  sterilising  action,  with  water 
in  which  bacterium  coli  and  similar  bacteria  have  been  dis- 
seminated. The  maintenance  of  the  working  regulations  must 
be  controlled  from  time  to  time  by  an  electrical  engineer. 

The  cost  of  sterilising  water  in  Paderborn  ranges,  according 
to  Schreiber,  from  o-43d.  to  i-5d.  per  1000  gallons  without  pre- 
liminary filtration,  and  with  nitration  from  o-66d.  to  i'94d.  per 
1000  gallons. 

At  the  Parisian  works,  according  to  Rideal,  1-31  kilowatts 


24  WATER   PURIFICATION 

current  were  necessary  to  sterilise  100  cubic  metres  of  water.  The 
total  cost,  exclusive  of  the  repayment  of  loans  and  payment 
of  interest,  amounted  to  o-33d.  per  1000  gallons. 

In  the  St.  Petersburg  undertaking  the  cost  of  working  is 
o-87d.  to  i-od.,  of  which  only  half  is  due  to  ozonisation. 

The  cost  of  sand  nitration,  according  to  Schreiber,  amounts  in 
comparable  cases  from  i-o5d.  to  i-87d.  per  1000  gallons. 

(b)  The  Disinfection  of  Drinking-Water  with  free  Chlorine. 

In  the  year  1894  it  was  shown  by  Traube  that,  by  treatment 
with  very  small  amounts  of  free  chlorine,  the  bacteria  in  water 
could  be  destroyed.  Later  investigations  by  other  authors 
showed  that  for  certain  destruction  of  the  bacteria  the  amounts 
of  chloride  of  lime  must  be  greater.  The  process  remained  thus 
for  a  long  time,  but  was  eventually  taken  up  again  in  practice 
several  years  ago.  Recently,  however,  the  method  has  been 
extensively  applied,  especially  in  America. 

The  Duyk  Ferric  Chloride  Process,  Howatson  System 
(Thumm  and  Schiele). 

In  this  process  the  raw  water,  either  during  or  immediately 
after  the  sedimentation  of  the  undissolved  particles,  is  treated 
with  a  solution  containing  chloride  of  lime,  and  then  with  one 
of  ferric  chloride.  The  mixture  is  led  on  to  a  mechanical  filter 
(Howatson  system)  without  further  sedimentation,  or  with  an 
intermediate  disposition  of  sedimentation  arrangements  ;  the 
filtered  water  is  then  ready  for  use. 

By  the  addition  of  the  chemicals  the  following  reactions  take 
place  : 

6  CaOCl2  +  Fe2Cl6=6  CaCl2+Fe2O3+3  C12O. 
3ClaO=3Cl2+30. 

The  resulting  chlorine  and  oxygen  act  as  disinfectants,  whilst 
the  voluminous  ferric  hydroxide  and  the  calcium  carbonate, 
resulting  from  the  decomposition  of  the  calcium  chloride,  draw 
the  suspended  matter  along  with  them  to  the  bottom  on  settling. 

In  Middelkerke,  in  Belgium,  the  method  is  in  practical  applica- 
tion ;  there,  and  later  in  Paris,  it  has  been  tested.  The  con- 
clusions are  favourable.  The  destruction  of  the  bacteria  must 
have  been  extensive. 


STERILISATION   PROCESSES  25 

Thumm  and  Schiele,  who  inspected  the  Middelkerke  under- 
taking, and  base  their  view  on  the  impressions  obtained  and  the 
accounts  received,  express  themselves  as  generally  favourable. 
In  the  ferric  chloride  process  it  may  be  important  to  consider 
that  the  chlorine  disappears  of  itself  after  some  time,  and  that 
the  water  treated  does  not  then  contain  any  harmful  chlorine 
compounds. 

(c)  Sterilisation  with  Chloride  of  Lime  or  Sodium  Hypochlorite. 

This  method,  according  to  Imhoff  and  Saville,  has  been  intro- 
duced in  considerably  more  than  one  hundred  American  towns. 
The  method  is  especially  suitable  in  those  places  where  the  water 
is  physically  good,  but  has  the  disadvantage  of  containing  either 
permanent  or  transitory  disease  germs. 

The  chloride  of  lime  is  generally  added  to  the  water  in  the 
proportion  of  i  part  to  350,000  parts  of  water  (which  means  i  part 
of  active  chlorine  per  1,000,000  parts  of  water). 

The  free  chlorine  acts  upon  the  bacteria,  more  especially  on 
those  which  communicate  disease. 

The  cost  of  the  process  is  very  moderate,  being  only  o-c27d. 
per  1000  gallons,  therefore  only  a  twentieth  the  cost  of  other 
purification  processes. 

The  method  is  not  applicable  where  much  suspended  matter, 
or  even  organic  matter,  or  iron,  is  present  in  the  water,  for  then 
the  free  chlorine  is  consumed  in  the  oxidation  of  these  substances. 

On  account  of  the  small  amount  of  bleach  added,  it  should  not 
be  necessary  to  displace  the  chloride  of  lime  from  the  water 
subsequently  ;  the  water,  also,  should  not  possess  any  appreciable 
taste  or  smell. 

Quite  recently  a  series  of  reports  upon  the  method  have  come 
from  English  and  American  towns. 

G.  A.  Johnson,  who  has  taken  up  the  process  again  in  America, 
declares  that  sodium  hypochlorite  can  be  used  as  well  as  bleach. 
The  following  are  mentioned  as  advantages  of  the  process  : 
the  rapidity  with  which  the  bacteria,  especially  pathogenic 
bacteria,  are  quickly  destroyed ;  the  ease  with  which  the  addition 
of  chemicals  can  be  adapted  to  any  change  in  the  water  ;  the 
absence  of  any  harmful  reaction  product  in  the  water ;  the 
rapidity  of  the  reaction. 


26  WATER   PURIFICATION 

The  bleach  treatment  is  useless  in  the  following  points  :  bac- 
teria spores  are  not  destroyed  ;  the  bacteria  embedded  in  the 
suspended  solid  particles  remain  unaffected. 

C.  Walker  reports  on  the  chloride  of  lime  water-purification 
process  called  the  De  Chlor  process,  which  was  tested  for  six 
months  on  an  experimental  scale.  The  De  Chlor  system  removes 
the  excess  of  chlorine  by  means  of  a  preparation  (charcoal) 
insoluble  in  water,  added  to  the  filter  in  granular  form.  The 
number  of  bacteria  fell,  after  passing  through  the  filter,  to 
between  234  and  421  per  cubic  centimetre  ;  the  purified  water 
contains  on  an  average  32  germs  per  cubic  centimetre.  Bac- 
terium coli  was  found  in  i  cubic  centimetre  of  raw  water,  in 
10  cubic  centimetres  of  the  first  filtrate,  and  in  the  pure  water 
was  no  longer  found  in  100  cubic  centimetres. 

According  to  Craven,  0-3  to  0-4  milligram  of  chloride  of  lime 
is  added  to  every  litre  (20  to  25  grains  per  1000  gallons)  of 
Ohama  water,  which  is  previously  treated  in  clarifying  basins. 
The  number  of  bacteria  is  thereby  reduced  by  about  97  per  cent. 
Bacterium  coli  could  only  be  found  in  isolated  cases.  In 
Minneapolis  from  1-54  to  3-04  milligrams  is  added  to  a  litre 
of  water.  The  number  of  bacteria  in  the  raw  water  sank  from 
between  250  and  8000  to  between  7  and  1200.  Bacterium  coli 
was  not  found  in  the  water  so  treated. 

In  the  opinion  of  the  author  it  is  of  advantage  to  use  the 
method  for  a  time  with  a  certain  amount  of  scepticism,  as  sus- 
picion almost  prescribes  that  to  be  certain  of  the  destruction 
of  all  the  bacteria  such  an  excess  of  bleach  is  necessary,  that  it 
is  noticeable  in  smell  and  taste,  or  vice  versa,  that  if  there  is 
no  smell  and  taste  in  the  purified  water  the  bacteria  are  not 
destroyed  with  certainty. 

Add  to  this  also  that  it  is  not  yet  established  that  the  con- 
tinued use  of  small  quantities  of  bleach,  even  should  they  be 
imperceptible  by  the  senses,  is  not  a  matter  for  serious  mis- 
givings. 

For  this  reason  this  method  cannot  be  recommended  for  general 
imitation.  It  might  possibly  be  of  service  in  certain  circum- 
stances, if  there  were  temporary  dangers  with  the  drinking- 
water,  as  in  times  of  epidemic,  or  it  might  perhaps  be  used  with 
success  in  time  of  war. 


STERILISATION   PROCESSES  27 

(d)  Sterilisation  of  Drinking-W ater  by  means  of  Ultra-Violet 

Light. 

It  is  well  known  that  if  white  light  be  analysed  into  its  com- 
ponents by  means  of  a  prism,  beyond  the  extreme  violet  end  of 
the  spectrum  there  can  be  indicated  certain  rays  which  cannot 
be  perceived  as  light  rays,  and  are  therefore  invisible,  but  to 
which  there  belong  powerful  chemical  activities,  e.g.  towards  a 
photographic  plate. 

That  these  ultra-violet  rays  also  possessed  the  power  of  killing 
bacteria  has  long  been  known.  Downes  and  Blunt,  two  English 
investigators,  observed  this  in  the  year  1877,  and  the  power  of 
sunlight  to  kill  bacteria  is  attributed  to  these  ultra-violet  rays. 
Ultra-violet  rays  are  to-day  generated  by  means  of  the  quartz 
mercury-vapour  lamp.  An  electric  current  is  sent  through 
mercury  vapour  which  is  enclosed  in  an  evacuated  quartz-tube  ; 
the  mercury  vapour  thereby  glows  and  sends  out  ultra-violet 
rays  which  have  the  property  of  passing  through  quartz  though 
they  are  retained  by  glass. 

The  real  discoverers  of  the  sterilisation  of  drinking-water 
by  means  of  ultra-violet  rays  are  the  French  workers,  Courmont 
and  Nogier.  In  their  experiments  a  lamp  was  fastened  in  the 
axis  of  a  cylinder  of  60  centimetres  diameter,  so  that  the  walls 
were  not  more  than  30  centimetres  distant  from  the  source  of 
the  light.  Only  clear  water,  without  turbidity  or  colour,  is 
sterilisable  in  this  manner.  The  lamp  is  purposely  immersed  in 
the  water.  In  the  first  place  the  sterilising  action  is  better  when 
the  lamp  is  immersed,  as  the  water  is  in  closer  contact  with  the 
source  of  the  rays,  and  all  the  rays  are  used  up  on  every  side. 
It  seems,  however,  to  be  also  necessary  to  immerse  the  lamp 
in  order  to  cool  it,  and  to  prevent  it  varying  on  account  of  heat 
changes.  It  was  formerly  thought  that  the  action  of  the  ultra- 
violet rays  rested  on  the  formation  of  hydrogen  peroxide  or  ozone. 
That  is  not  the  case  ;  such  compounds  could  never  be  shown 
to  be  present.  The  taste,  smell,  temperature,  and  chemical 
properties  of  the  water  are  in  no  way  altered  by  the  rays,  and 
protracted  experiments  on  animals  have  further  demonstrated 
the  complete  harmlessness  of  the  water  so  treated. 

The  sterilising  action,  as  communicated  by  Courmont  and 
Nogier,  is  good,  and  not  inferior  to  that  in  the  water-purification 


28  WATER   PURIFICATION 

methods  previously  mentioned.  Also  as  regards  economy,  the 
process,  according  to  the  accounts  of  Courmont  and  Nogier,  can 
bear  comparison  with  the  above  purification  methods. 

From  experiments  conducted  by  two  members  of  the  Konigl. 
Prufungsanstalt  fur  Wasserversorgung  und  Abwasserbeseitigung 
(Royal  Institute  for  the  Testing  of  Water  Supply  and  Sewage 
Disposal)  the  results  are  not  so  favourable  as  those  of  Courmont 
and  Nogier  in  all  points.  Grimm  and  Weldert  carried  out  their 
researches  with  the  mercury- vapour  lamp  of  the  Quartz  Lamp  Co., 
Ltd.,  Hanau-on-Maine.  They  collect  the  results  of  their  work  as 
follows  : — 

"  (i)  With  the  apparatus  tested  clear  water,  containing  few  bac- 
teria, can  be  sterilised  at  the  rate  of  0-55  cubic  metres  (120  gallons) 
per  hour  under  the  conditions  described  above.  Clear  water,  very 
rich  in  bacteria,  can,  on  the  other  hand,  only  be  rendered  sterile 
at  the  rate  of  0-45  cubic  metre  per  hour,  in  which  case  it 
does  not  make  any  difference  whether  the  bacteria  are  water 
bacteria  or,  with  pathogenic  bacteria,  coli  bacteria.  (2)  Turbidity 
of  the  water,  even  to  a  small  extent,  makes  disinfection  uncertain. 
With  a  high  degree  of  turbidity  the  destruction  of  bacteria  by 
the  lamp  is  impossible,  at  all  events  within  the  limits  which  come 
into  practical  consideration.  (3)  Likewise  the  yellow  colour  of 
water  due  to  colloids,  such  as  bog-water  shows,  acts  as  a  very 
great  hindrance.  Indeed,  with  only  a  slight  amount  of  coloration, 
the  hindrance  is  so  great  that  it  is  practically  impossible  to 
accomplish  disinfection  by  this  method.  (4)  The  water  is  not 
altered  in  any  physico-chemical  respects  by  its  passage  through 
the  experimental  apparatus,  with  the  exception  of  an  increase 
in  temperature  of  a  few  tenths  of  a  degree.  With  prolonged  action 
of  the  rays,  further  increases  of  temperature  result,  as  well  as 
symptoms  of  chemical  decomposition.  (5)  The  expenses  of 
water  purification  by  means  of  ultra-violet  light,  reckoned  on  the 
basis  of  the  researches,  are,  comparatively  speaking,  very  high, 
and  cannot  bear  comparison  with  the  cost  of  the  methods  of  water 
purification  employed  at  the  present  time  on  a  large  scale." 

Erlwein  reports  on  the  experience  of  the  firm  of  Siemens  and 
Halske  in  this  respect.  The  energy  required  is  greater  than  in 
sterilisation  with  ozone.  With  regard  to  the  other  factors,  a  com- 
parative estimate  of  the  cost  of  working,  under  the  conditions 
operative  in  a  central  waterworks  undertaking,  is  wanting  in  the 


STERILISATION   PROCESSES  29 

case  of  the  ultra-violet  light  method,  and  especially  the  most 
important,  viz.  a  more  exact  knowledge  of  the  deterioration 
and  cost  of  repairs  of  the  still  very  expensive  quartz  lamps. 

Buywid  is  of  the  opinion  that  the  ultra-violet  light  method  is 
more  promising  than  the  ozone  method. 

To  the  knowledge  of  the  author  the  method  has  not  been  to 
the  present  applied  on  a  large  scale.  Mercury-vapour  quartz 
lamps  are  supplied  by  different  firms,  e.g.  The  Ultra- Violet  Firm, 
22  Rue  Chanchat,  Paris  ;  Westinghouse,  Cooper,  Hewitt  and 
Co.,  131  Wilhelmstrasse,  Berlin,  the  Quartz  Lamp  Co.,  Ltd., 
Hanau-on-Maine. 

Taking  into  consideration  the  fact  that  the  water  is  not  in  any 
way  changed  as  regards  its  nature,  and  that  extended  researches 
with  animals  have  shown  that  water  acted  upon  by  the  rays  even 
for  a  long  time  is  not  harmful,  the  method  should  have  a  future 
if  the  cost  can  be  reduced. 

In  addition  to  their  researches  on  the  ultra-violet  light  method, 
Grimm  and  Weldert  collected  together  the  costs  of  the  principal 
water-purification  methods.  Nos.  i  to  4  of  the  following  table 
are  the  averages  of  estimates  of  various  undertakings  on  a  large 
scale.  No.  5  is  reckoned  on  the  basis  of  the  experiments  of 
Grimm  and  Weldert. 

Cost  per  1000  gallons 
List  of  the  various  Processes.  of  purified  water. 

(1)  Slow  Sand  Filters. 

Cost  of  working  ....  o-6id. 

Total  cost  .....  5*2d. 

(2)  Mechanical  Filters. 

Cost  of  working            ....  2-8d- 

Total  cost 5-8d. 

(3)  Ozone  Plants. 

Cost  of  working            ....  2-8d. 

Total  cost 8.2d. 

(4)  Chloride  of  Lime  Plants. 

Cost  of  working  (Johnson)    .          .          .  o-o7d. 

Total  Cost  (Johnson,  Imhoff,  and  Saville)        o-34d. 

(5)  Ultra-violet  light  plant. 

Cost  of  working  : 

100%  Bacteriological  Effect          .          .        145.  6d. 

99  to  99-9%  „      .  55.  to  73.  3d. 


30  WATER   PURIFICATION 

(e)  Disinfection  of  Water- Mains  and  Wells. 

If  an  epidemic  reigns  in  a  town,  and  there  are  grounds  for 
believing  that  the  contagion  is  to  be  attributed  to  drinking- 
water,  the  disinfection  of  the  water-mains  is  to  be  recommended, 
especially  in  those  cases  in  which  a  fresh  drinking-water,  free 
from  any  objection,  must  be  led  into  the  infected  main.  Fliigge 
and  Bischoff,  during  a  typhoid  epidemic  in  Beuthen  (Upper 
Schleswig),  employed  for  this  purpose  a  0-2  per  cent  solution  of 
sulphuric  acid.  The  acidified  water  remained  standing  in  the 
main  many  hours.  The  strength  of  the  sulphuric  acid  in  the  water 
is  controlled  at  the  stop-cocks.  In  an  epidemic  of  typhoid  fever 
in  Gelsenkirchen,  in  the  year  1901,  the  mains  were  likewise  dis- 
infected with  sulphuric  acid. 

With  wells  which  in  general  are  suitably  situated  and  lie  in 
surroundings  free  from  objection,  but  which  seem  to  be  infected 
from  above,  it  is  possible,  according  to  a  proposal  of  M.  Neiszer, 
to  introduce  compressed  steam  (5  atmospheres)  ;  the  whole 
contents  of  the  well  are  thereby  brought  to  the  boiling-point. 

The  same  method,  or  disinfection  with  "  Carbolic-Sulphuric 
acid  "  (Frankel),  which  is  subsequently  pumped  away,  can  be 
applied  in  the  preliminary  works  of  a  central  water  supply  for 
disinfecting  borings,  so  as  to  be  able  to  take  away  samples 
bacteriologically  free  from  objection. 


(iii)  Purification  of  Water  in  directions  other  than  that  of  Health. 

As  already  mentioned,  substances  occasionally  appear  in  water 
which,  without  being  detrimental  to  health,  still  cause  great 
trouble,  since,  as  with  iron  and  manganese,  they  may  discolour 
the  water,  or,  as  with  free  carbonic  acid,  may  attack  the  walls 
of  pipes  and  reservoirs. 

(a)  Removal  of  Iron. 

Ground-waters  of  the  diluvial  and  alluvial  strata  of  the  North 
German  Lowland  often  contain  iron  in  greater  or  lesser  quantities, 
as  ferrous  carbonate  or  the  ferrous  salt  of  humic  acid.  When 
freshly  drawn  the  water  is  generally  clear,  but  becomes  turbid 
after  some  time  owing  to  the  separation  of  a  brown  precipitate, 


OTHER   PROCESSES  81 

since  the  oxygen  of  the  air  converts  the  ferrous  salt  into  in- 
soluble ferric  hydroxide  with  evolution  of  carbon  dioxide. 

Although  this  turbidity  due  to  iron  is  objectionable  not  so 
much  from  the  point  of  view  of  health  as  from  that  of  appearance, 
still  it  frequently  causes  trouble.  The  flocculent  hydroxide, 
settling  in  the  pipes  and  reservoirs,  renders  their  frequent  cleans- 
ing necessary.  Further,  the  presence  of  iron  in  water  favours  the 
appearance  of  numerous  micro-organisms  which  store  up  iron, 
especially  the  iron  bacteria,  which  decompose  and  evolve  odours 
of  sulphuretted  hydrogen  and  other  decomposition  products, 
and  gives  to  the  water  a  specific  metallic  taste. 

Such  water  is  not  suitable  for  most  technical  purposes. 

A  few  tenths  of  a  milligram  of  iron  in  a  litre  of  water  may  make 
an  iron-removal  plant  necessary,  since  iron  bacteria  thrive  best 
in  waters  weak  in  iron. 

The  methods  of  removing  the  iron  are  based  on  three  physico- 
chemical  actions. 

First,  by  contact  of  dissolved  ferrous  iron  with  air,  oxygen 
converts  the  ferrous  compound  into  insoluble  ferric  compounds. 
Consequently  the  water  may  be  aerated,  and  subsequently  filtered. 

Secondly,  since  carbonic  acid  keeps  the  iron  in  solution,  the 
precipitation  of  the  iron  may  be  effected  by  neutralisation  of  the 
carbonic  acid  with  lime. 

Finally,  if  the  iron  is  present  in  the  water  in  colloidal  form 
(organically  combined),  a  coagulant,  such  as  aluminium  sulphate 
or  ferric  chloride,  is  employed. 

The  last  method  is  often  used  in  America,  whilst  in  Germany  all 
processes  for  the  removal  of  iron  are  based  upon  aeration  and 
filtration. 

The  method  of  effecting  this  aeration  and  filtration  varies 
considerably  with  different  systems. 

Aeration  is  effected  by  allowing  water  to  fall  through  the  air, 
cascades  (Elbing),  by  means  of  raining  devices  using  perforated 
troughs  (Wismar),  in  coke-towers  (Piefke),  over  wood  (Berlin), 
over  clinkers  (Delitzsch),  over  glazed  brick  (Sternberg),  and  in 
other  ways. 

Similarly,  the  method  of  filtration  varies.  In  general,  sand  and 
gravel  have  proved  the  best  media  for  filtration.  The  size  of  the 
grains  of  sand  is  an  important  factor  in  the  formation  of  the  filter 
layer,  and  in  the  complete  retention  of  the  ferric  hydrate  particles. 


32  WATER   PURIFICATION 

The  method  of  cleaning  the  filter  and  aerator  is  also  different 
in  the  various  systems. 

In  the  following  review  of  the  most  important  methods  for 
removing  iron  are  also  included  those  which  are  used  mainly 
for  industrial  purposes,  since  they  are  based  on  the  same  principles 
and  are  conducted  in  precisely  the  same  way  as  are  the  larger 
undertakings  for  central  water  supply.  The  removal  of  iron 
from  single  wells,  on  the  other  hand,  will  be  specially  treated  on 
page  49. 

The  most  important  systems  for  the  removal  of  iron  are 
characterised  as  follows  (Schwers)  :— 

1.  Piefke  system  :   One  of  the  oldest  and  best  systems.     The 
water  containing  iron  is  brought  to  the  coke-tower,  a  cylindrical 
upright  vessel,  filled  with  pieces  of  coke  the  size  of  a  man's  fist. 
The  water  flows  slowly  over  the  coke  and  passes  into  a  settling- 
tank  situated  underneath,  whence  it  flows  on  to  a  sand  filter, 
which  is  arranged  on  the  usual  lines.    The  coke-tower  is  cleaned 
by  flushing  in  the  reverse  direction.    It  should  only  be  necessary 
to  refill  the  tower  once  or  twice  each  year.    These  Piefke  towers 
are  largely  used,  and  have  proved  excellent. 

2.  Oesten   system:    A  raining    arrangement    (2  m.  rainfall), 
with  roses,  and  filtration  through  gravel  the  size  of  wheat-grains. 

3.  Kurth  system  :  Violent  rainfall  and  gravel  filtration,  worked 
by  the  stroke  of  a  piston  ;  for  small  plants. 

4.  Bieske  system  :  Analogous  to  the  previous  one. 

5.  Thiem  system:   Raining  arrangement  with  perforated  trays. 

6.  Reichling  system  :    Raining  arrangement  with  centrifuge 
or  sieve,  closed  filtration  upwards,  under  pressure,  through  layers 
of  sand,  gravel,  and  wood-wool ;  used  in  industry. 

7.  Koerting  system  :   Similar  to  the  previous  one. 

8.  Pfeiffer  system  :   Simple  aeration  and  sand  filtration. 

9.  Wingen  system  :    Waterfalls,  sand  filtration. 

10.  Taacks  system  :    Waterfalls,  sand  filtration. 

11.  Krohnke  system  :    Coke-tower,  rotating  cylindrical  filter 
that  is  alternately  filled  with  sand  and  water. 

12.  Lanz  system  :   Filtration  through  natural  sandstone. 

13.  Fischer  system  :    Filtration  through  porous  artificial  stone 
(Wormser  Kunststein). 

14.  Agga  system  :    Filtration  through  pipes  of  artificial  stone 
in  the  sand  filter,  purification  by  a  reverse  stream  of  water. 


OTHER   PROCESSES  33 

15.  Reiser!  system  :   Filtration  in  the  open  air  through  gravel, 
with  or  without  previous  aeration  over  coke  ;    cleansing  by  a 
reverse  stream  of  water. 

16.  Bollmann  system  :  Gravel  filtration  under  pressure  without 
previous   aeration,   purification   by   a  stream   of  water  in   the 
reverse  direction. 

17.  Breda  system  :    Filtration  under  pressure  through  "  Ton- 
koks  "  (clay-coke)  and  gravel  of  various  sizes,  after  preliminary 
aeration  in  a  mixer  ;  purification  by  a  reverse  stream  of  water. 

18.  Helm   system  :     Filtration   through   brown   iron-ore   slag 
in  which  aeration  takes  place  by  means  of  occluded  oxygen  ; 
purification  by  reversing  the  water  current. 

19.  Biihring   system  :     Filtration,    as   in   the   previous   case, 
through  bone  charcoal ;    purification  with  dilute  hydrochloric 
acid  ;   for  domestic  purposes. 

20.  Buttner  system  (von  der  Linde  and  Hesz)  :  Filtration  under 
pressure  through  wood  shavings,  impregnated  with  tin  oxide 
without  any  special  aeration  ;   purification  by  reversal  of  stream. 

21.  Bock  system  :    Filtration  analogous  to  the  previous  one, 
through  wood-wool. 

22.  Sellenscheidt    system :     Raining    arrangement,    filtration 
through  plant-fibre  ;  used  especially  in  breweries. 

23.  Dehne  system  :     Aeration   by  raining  with   an  injector, 
addition  of  milk  of  lime,  filtration  under  pressure  through  felt 
discs  ;   used  in  industrial  concerns. 

24.  Jewell  system  :     Rapid  sand  filtration  with  or  without 
addition  of  milk  of  lime  and  sulphate  of  alumina,  unaccompanied 
by  any  aeration.    This  system  was  introduced  in  Posen,  in  1909, 
producing  30,000  cubic  metres  per  day.    No  chemicals  are  added  ; 
the  water  is  freed  from  iron  by  simple  filtration. 

25.  "  Voran  "    system  :     Frankfort-on-Maine.      Aeration    in 
the  closed  system  by  compression  through  nozzles,  in  the  open 
system  by  sprinkling  over  a  cataract-like  erection  of  coke,  bricks, 
etc.     An  open  and  a  closed  "  Voran  "  plant  are  pictured  in 
Figures  6  and  7.     The  figures  are  intelligible  without  further 
explanation. 

Plants  for  the  removal  of  iron  are  built  both  open  and  closed. 

Closed    systems    offer    greater    protection,    naturally,    against 

infection  of  the  water  by  bacteria  ;    still,  according  to  Schwers, 

plants  with  open  apparatus  have  proved  as  good  as  the  closed 

D 


34  WATER   PURIFICATION 

from  the  bacteriological  point  of  view.  In  recent  years  a  vehe- 
ment dispute  has  been  in  progress  with  reference  to  the  greater 
or  lesser  suitability  of  the  open  and  closed  systems.  Both  systems 
have  been  equally  praised  and  criticised.  On  the  whole  they  may 
be  regarded  as  of  equal  value. 

The  efficiency  of  iron-removal  plants  depends  upon  the  height 
of  the  aerator  and  filter,  the  velocity  during  aeration  and  filtra- 
tion, and  other  technical  points. 


FIG.  6.     OPKN  PLANT  FOR 

THE  REMOVAL  OF  IRON. 

"  VORAN"  SYSTEM. 


FIG.  7.     CLOSED  PLANT  FOR  THE  REMOVAL  OF 
IRON.     "  YORAN  "  SYSTEM. 


The  height  of  the  aerator  is  generally  about  3  to  7  metres  ; 
the  velocity  of  filtration  in  open  systems  seldom  amounts  to  more 
than  i  metre,  in  closed  systems  it  is  often  10  metres  (per  hour) . 

The  pressure  is  generally  produced  by  the  difference  in  level 
between  the  surface  of  water  in  the  filter  and  in  the  pure-water 
reservoir. 

Good  iron-removal  plants  yield  a  water  which  at  most  still 
contains  o-i  milligram  iron  per  litre. 

The  cost  of  removing  iron  from  water  amounts  in  a  series  of 
German  towns  from  0-04  to  o-^d.  per  1000  gallons. 


OTHER   PROCESSES  35 

(b)  Removal  of  Manganese. 

As  a  result  of  the  water  calamity  in  Breslau  in  the  year  1906, 
general  attention  has  been  turned  to  the  occurrence  of  manganese 
salts  in  water.  Although  only  present  in  small  amounts,  they 
deposit  a  weak  scum  which  makes  the  water  insipid,  stains  linen 
and  paper,  pollutes  the  reservoirs  in  breweries,  injures  the  com- 
plete action  of  yeast,  etc.  Certain  micro-organisms  absorb  it 
to  a  still  greater  degree  than  iron.  Manganese  almost  always 
accompanies  iron,  but  the  amount  is  generally  so  small  that  its 
presence  in  the  majority  of  cases  does  not  approach  practical 
importance  at  all. 

Proska*uer  was  the  first  to  point  out  the  occurrence  of  man- 
ganese salts  in  water. 

Manganese  is  removed  by  aeration,  like  iron,  but  it  separates 
out  with  greater  difficulty,  since,  during  aeration,  mangani- 
manganous  compounds  result,  which  are  soluble  to  a  considerable 
extent  in  water. 

The  calamity  in  Breslau  originated  in  consequence  of  the 
existing  geological  conditions.  Iron  and  manganese  sulphides, 
in  the  humous  layers  situated  over  the  ground-water,  were 
converted  to  sulphates  by  oxidation  and  then  passed  into  the 
ground-water  owing  to  a  flood  which  inundated  the  whole  tract 
of  country. 

For  the  removal  of  manganese,  and  also  of  iron,  Permutit  has 
recently  been  recommended.  Permutit  is  an  artificially  prepared 
product  (aluminium  silicates),  principally  employed  in  the 
softening  of  water  (see  page  60) . 

Permutits  have  the  property  of  withdrawing  from  water, 
lime,  magnesia,  iron,  and  manganese,  in  exchange  for  sodium, 
if  the  water  be  allowed  to  flow  over  them.  Luhrig  and  Becker, 
Gaus  and  Noll,  have  carried  out  experiments  on  the  removal  of 
manganese  by  means  of  calcium  permutit.  The  manganese  is 
thereby  exchanged  for  calcium.  Whilst  Luhrig  and  Becker 
obtained  good  results  in  laboratory  experiments,  a  trial  on  a  large 
scale  proved  a  failure.  The  water  took  from  the  permutit  sub- 
stances which  imparted  to  it  an  alkaline  reaction,  causing  a 
precipitation  of  manganese  as  oxyhydrate.  This  precipitate 
choked  up  the  filter.  Noll  found  on  an  experimental  scale  that 
manganese  was  quantitatively  removed  from  water  by  calcium 


36  WATER   PURIFICATION 

permutit,  so  long  as  the  content  of  the  permutit  in  manganese 
was  less  than  2  per  cent.  The  cost  of  removing  manganese  with 
calcium  permutit  is  estimated  by  Noll  to  be  o-ogd.  per  1000 
gallons. 

Quite  recently  the  Permutit  Filter  Company,  Berlin,  have  recom- 
mended a  new  method  for  removing  manganese  and  iron  by  means 
of  permutit.  According  to  Kriegsheim,  the  method  is  as  follows  : 
From  a  suitable  permutit,  e.g.  sodium  permutit,  a  manganese 
permutit  is  prepared  by  treatment  with  a  solution  of  manganese 
chloride.  This  manganese  permutit  is  then  treated  with  potassium 
permanganate.  The  permanganic  acid  is  thereby  easily  combined 
with  the  manganese  oxide  of  the  permutit  to  form  highly  oxidised 
manganese  compounds.  If  a  water  containing  manganese  be  now 
filtered  through  a  permutit  filter  so  treated,  these  higher  oxides 
of  manganese  can  very  rapidly  effect  complete  removal  of  the 
manganese,  even  with  rapid  velocity  of  filtration.  -The  action 
is  based  upon  the  fact  that  the  oxygen  necessary  for  the  oxidation 
process  is  presented  to  the  manganese  separating  out  during  the 
nitration  of  the  water  in  the  solid  condition  and  easily  split  off 
from  the  highly  oxidised  manganese  oxides.  The  oxidation 
causes  the  precipitation  of  the  manganese  in  the  water  in  an 
insoluble  form.  Should  the  action  diminish,  the  filter  can  be 
regenerated  by  means  of  a  2  to  3  per  cent  solution  of  perman- 
ganate. The  cost  of  this  process  should  be  very  small. 

As  already  mentioned,  the  process  is  not  only  recommended  for 
removal  of  manganese,  but  also  for  the  removal  of  iron.  The 
principle  is  the  same  in  the  latter  case  also. 

(c)  Removal  of  free  Carbon  Dioxide. 

If  water  contains  much  free  carbon  dioxide,  it  exercises  a  very 
deleterious  action  on  the  various  materials  required  in  water- 
works. Thus  it  was  observed,  for  example,  at  Frankfort-on- 
Maine,  that  a  newly  constructed  deep  reservoir  made  of  reinforced 
concrete  was  strongly  corroded  by  the  water.  Similarly  the  iron 
pipes  were  vigorously  attacked. 

Whilst  the  action  of  the  water  on  these  materials  is  more  a 
matter  of  economy  than  of  hygiene,  the  corrosion  of  lead  pipes, 
which  are  used  in  most  cases  for  the  conveyance  of  water  inside 
houses,  is  in  the  highest  degree  serious  from  the  point  of  \  iew  of 


OTHER   PROCESSES  37 

health,  since  lead  passes  into  the  drinking-water  as  a  result  and 
is,  even  in  the  smallest  quantities,  inimical  to  health. 

In  practice  three  methods  are  used  for  the  removal  of  free 
carbonic  acid. 

i.  The  water  is  allowed  to  flow  through  limestone  (Heyer- 
Scheelhaase)  .  The  free  carbonic  acid  is  thereby  converted  into 
calcium  bicarbonate  according  to  the  following  equation  : 

2O  +  CO2==Ca(HCO3)2. 


By  this  method,  therefore,  hardness  due  to  carbonates  is  in- 
creased. Where  the  water  is  of  itself  very  soft  this  increase  in 
hardness  is  not  harmful,  and  may  even  be  desirable.  If,  however, 
the  water  is  already  fairly  hard,  the  increase  in  hardness  might 
be  a  disadvantage.  Besides,  the  removal  of  carbon  dioxide  by 
means  of  limestone  is  not  accomplished  in  such  cases,  or  only 
incompletely.  The  method  is  in  use  on  a  large  scale  in  Frankfort- 
on-Maine  for  the  removal  of  the  free  carbonic  acid  from  Stadt- 
wald  water  of  1-5°  hardness,  and  containing  30  milligrams  CO2 
per  litre.  It  had  caused  great  trouble  in  the  new  deep  reservoirs 
of  Sachsenhaus,  and  also  in  the  mains.  The  hardness  of  the  water, 
when  freed  from  acid,  amounts  to  about  5°. 

As  the  Frankfort  plant  for  removing  carbonic  acid  has  proved 
excellent,  it  may  be  shortly  described  as  follows  (see  Fig.  8)  :  — 

In  the  years  1906-7  the  plant  for  removing  carbon  dioxide 
was  erected  at  a  cost  of  78,000  marks  (about  £3900)  in  the 
Chamber  A  of  the  deep  reservoirs  of  the  Sachsenhaus  plant. 

Seven  of  the  ten  passages  of  the  chamber  were  employed  for 
the  neutralising  process.  The  first  serves  as  an  inlet  chamber, 
the  second  and  third  as  sand  filters,  and  the  four  following  as 
limestone  scrubbers. 

From  the  inlet  chamber  the  water  is  distributed  through  per- 
forations in  the  partition-wall  on  to  the  sand  filter,  which  only 
serves  to  retain  the  particles  of  ferric  oxide  carried  along  out  of 
the  pressure  tubes.  The  velocity  of  filtration  amounts  to  80  m. 
in  24  hours.  The  filtered  water  passes  through  openings  to  the 
base  of  dividing-  wall,  and  with  the  help  of  distributors  passes 
under  the  limestone  scrubber.  The  limestone  scrubber  is  com- 
posed of  a  layer  of  flints  at  the  bottom,  over  which  rests  a  layer 
of  gravel,  and  then  four  layers  of  limestone  in  different  states  of 
division,  namely,  about  the  size  of  walnuts,  beans,  peas,  and 


38  WATER   PURIFICATION 

coarse  sand.  Each  of  the  first  three  layers  is  3  inches  high,  the 
height  of  the  fourth  being  2  feet.  The  velocity  of  water  in  the 
scrubber  reaches  40  metres  (130  feet)  in  24  hours.  The  water, 
when  neutralised,  flows  partly  through  an  opening  in  the  partition- 
wall  between  sections  7  and  8  to  the  last  three  sections  of  Chamber 
A,  and  partly  through  a  special  pipe  to  Chambers  B,  C,  and  D 
of  the  reservoir.  About  every  three  months  the  sand  filter  has  to 
be  cleaned,  by  being  washed  through  with  water  in  the  reverse 
direction  from  the  bottom  upwards. 

With  about  5,000,000  gallons  of  water  neutralised  daily, 
approximately  ij  tons  of  limestone  are  dissolved  by  the  water 
and  carried  away. 

2.  Caustic  soda,  or  sodium  carbonate,  is  added  to  the  water 
in  calculated  amount,  according  to  the  estimation  of  carbonic  acid 
(Heyer).    The  free  carbonic  acid  is  converted  to  the  bi-carbonate. 

CO2+H2O+Na2CO3-^2  NaHCO3. 

This  method  was  introduced  by  Heyer  to  neutralise  the  drinking- 
water  in  Dessau.  In  the  eighth  decade  of  last  century  a  large 
number  of  persons  became  ill  through  lead  poisoning.  Heyer 
perceived  that  the  capacity  to  dissolve  lead  was  due  to  the 
amount  of  free  carbonic  acid  present.  After  various  other 
experiments  he  finally  proposed  the  neutralisation  of  the  water 
with  caustic  soda  and  sodium  carbonate. 

There  are  many  types  of  apparatus  for  measuring  the  amount 
of  chemicals  to  be  added.  It  is  stated  and  agreed  concerning 
this  method  that  it  makes  the  carbonic  acid  quite  harmless.  The 
general  public,  however,  has  generally  an  instinctive  aversion 
towards  a  drinking-water  treated  with  chemicals.  This  fact  is, 
doubtless,  the  main  objection  to  this  otherwise  good  system. 

3.  If  a  water  containing  carbon  dioxide  is  allowed  to  rain 
down  in  a  fine  state  of  division,  or  allowed  to  trickle  slowly  over 
coke,  glass,  gravel,  etc.,  it  is  freed  from  carbon  dioxide. 

With  larger  amounts  of  carbon  dioxide  present,  the  raining 
process  has  to  be  repeated  many  times  to  remove  the  carbonic 
acid.  Further,  the  Jieight  of  the  fall  has  an  influence.  The 
removal  of  carbon  dioxide  in  this  way  is  disadvantageous  for  the 
reason  that  the  water  is  greatly  enriched  with  oxygen.  A  water 
rich  in  oxygen  is  also  not  good  as,  in  its  turn,  it  causes  severe 
rusting  of  the  iron  pipes. 


40  WATER   PURIFICATION 

H.  Wehner  has  now  advanced  the  idea  of  effecting  the  trickling 
process  in  a  vacuum.  According  to  the  accounts  of  the  inventor, 
not  only  ought  the  carbon  dioxide  to  be  removed  more  rapidly, 
and  with  less  height  of  fall  necessary,  but  also,  simultaneously, 
the  amount  of  oxygen  should  be  considerably  diminished. 

Wehner's  vacuum  process  is  to  be  used  in  some  English  and 
German  towns. 


II.  PURIFICATION  OF  DRINKING-WATER  ON  A 
SMALL  SCALE. 

The  greatest  advantage  of  a  central  water  supply  is  this,  that, 
owing  to  the  size  of  the  project,  there  are  more  extensive  pre- 
liminaries for  securing  a  water  free  from  any  objection,  greater 
certainty  for  carrying  out  the  process  according  to  conditions, 
and  greater  possibility  of  expert  supervision  of  the  process, 
so  that  disturbances  are  easily  recognised  and  prevented. 

Over  and  above  this  there  exists  in  all  small-scale  purification 
processes  the  main  weakness  that  the  points  of  preference  named 
above  with  regard  to  large-scale  operations  are  either  non- 
existent or  are  not  sufficiently  assured. 

Isolated  houses,  estates,  establishments,  etc.,  would  do  well, 
therefore,  to  choose  for  their  water  supply,  water  free  as  far  as 
possible  from  any  objection,  and  not  needing  any  purification. 

Should  unforeseen  circumstances  intervene,  making  the  water 
of  a  central  water  supply,  or  even  a  single  supply,  seem  doubtful, 
then  methods  of  purification  on  a  small  scale  can  find  application. 
Of  first  importance  is  boiling  of  the  water  before  use. 

Moreover,  the  employment  of  purification  apparatus  on  a  small 
scale  is  to  be  regarded  as  a  makeshift,  since  it  should  be  con- 
stantly controlled  to  determine  whether  it  works  well  and 
continuously.  This,  naturally,  in  the  majority  of  cases,  cannot 
be  accomplished. 

Circumstances  like  epidemics,  war,  journeys  in  unknown  or 
quite  uncivilised  lands,  constitute  an  exception.  In  such  cases 
it  is  often  impossible  to  procure  water  free  from  objection.  The 
small  amount  of  water  necessary,  comparatively  speaking,  on 
such  occasions  can  be  purified  with  sufficient  certainty  by  the 
aid  of  purification  methods  on  a  small  scale.  This  is  all  the  more 


SMALL   OR   HOUSEHOLD   FILTERS  41 

true  when,  as,  for  example,  in  wars,  or  in  times  of  epidemic, 
the  necessary  personnel  is  at  one's  disposal.  The  observance  of 
the  regulations  can  then  be  supervised. 

This  review  of  apparatus  for  water  purification  on  a  small 
scale  naturally  refers  only  to  methods  which  aim  at  the  removal  of 
bacteria.  Of  apparatus  for  removing  substances  prejudicial  to 
the  appearance  of  the  water,  such  as  iron,  etc.,  there  are  also 
many  on  a  small  scale,  as  already  set  forth  above,  and  it  appears 
that  the  small  apparatus  has  the  same  action  as  the  corresponding 
apparatus  on  the  large  scale. 

(i)  Purification  by  means  of  Small  or  Household  Filters. 

The  household  filter  serves  a  double  purpose  :  firstly,  it  removes 
suspended  matter  and  makes  the  water  clear  ;  secondly,  it  is 
used  for  retaining  bacteria  also.  Household  filters  are  much 
less  germ-tight  than  sand  filters.  The  bacteria  are  washed 
through  the  filter  if  it  is  not  very  frequently  cleaned,  and  not 
infrequently  does  it  happen  that  the  filtered  water  is  richer  in 
bacteria  than  the  raw  water.  Small  filters,  therefore,  are  to  be 
used  with  great  caution. 

The  number  of  different  forms  of  domestic  filters  is  legion. 
They  are  all  based  on  the  filtration  of  the  water  through  some 
porous  material  with  or  without  the  employment  of  increased 
pressure.  Von  Esmarch  divides  them  into  the  following  groups :  — 

(a)  Charcoal  Filters. 

These  are  the  oldest  form  of  apparatus  of  this  kind.  They  are 
composed  of  plastic  retort  carbon  or  finely  sieved  charcoal, 
powdered  coke,  and  compounds  of  the  most  varied  preparations. 
They  generally  cost  between  30  and  70  shillings  each. 

Charcoal  filters  are  scarcely  used  nowadays,  since  their  bacterio- 
logical effect  is  practically  nil.  Indeed,  if  a  charcoal  filter  is  in  use 
for  some  time,  the  filtrate  is  often  worse  than  the  raw  water,  since 
the  bacteria  which  have  remained  behind  in  the  charcoal  have 
increased  considerably,  and  are  then  carried  along  with  the 
stream  of  water  passing  through.  Also,  as  regards  the  removal 
of  turbidity  these  filters  are  of  little  use. 


42  WATER   PURIFICATION 

(b)  Stone  Filters  of  Sandstone,  Pumice,  and  the  like. 

The  stone  is  burnt  from  coarse  or  fine  sand,  quartz,  lime,  and 
magnesium  silicates.  For  filters  that  work  without  pressure 
coarse  material  is  used,  whilst  for  pressure  filters  extremely  fine 
material  is  employed. 

The  clarification  of  the  water  may  be  rather  good  with  such 
apparatus.  The  bacteria,  on  the  other  hand,  go  through  the 
filter  fairly  readily,  at  the  latest  after  two  or  three  days.  The 
productivity  of  the  filters  is  generally  small,  usually  about  i  litre 
per  hour.  Frequently  the  yield  falls  off  quickly  also,  and  cleaning 
then  becomes  necessary. 

(c)  Asbestos  Filters. 

Asbestos  of  very  fine  fibre  is  used  as  the  filtering  medium,  and 
is  employed  as  a  pulp,  or  compressed  or  mixed  with  other 
materials.  Asbestos  filters  are  also  used  in  technical  work  for  the 
filtration  and  clarification  of  turbid  liquids  (beer,  oil,  wine,  etc.), 
and  for  the  retention  of  ferric  oxide  in  iron-removal  plants. 

The  filter  of  C.  Piefke  and  the  micro-membrane  filter  of  Fried- 
rich  Breyer  are  capital  asbestos  filters.  Asbestos  filters  retain 
bacteria  fairly  well ;  but  in  general  they  choke  up  very  quickly  ; 
this  necessitates  frequent  cleaning  and  sterilisation  of  the  appara- 
tus, which  takes  up  much  time. 

According  to  Gartner,  Breyer's  micro-membrane  filter  ought 
to  be  germ-tight. 

Good  asbestos  filters  are  supplied  by  the  firm  of  Arnold  and 
Schirmer,  123  Grosze  Frankfurter  Strasze,  Berlin,  N.O.,  or  by 
H.  Jensen  and  Co.,  20  Reichenstrasze,  Hamburg. 

(d)  Clay  Filters. 

Of  these  filters  there  are  likewise  a  number  of  different  speci- 
mens as,  for  example,  those  of  Olschewski  and  Hesse.  They  only 
filter  free  from  bacteria  for  a  short  time.  The  greater  the  yield 
of  water  the  shorter  time  are  they  germ-tight. 

(e)  Porcelain  Filters. 

The  principal  example  of  this  type  of  filter  is  the  Chamberland 
Filter.  It  consists  of  a  metal  cylinder,  which  can  be  screwed  on 


SMALL   OR   HOUSEHOLD   FILTERS  43 

to  the  water-tap.  Inside  the  cylinder  there  is  fastened  an  inner 
hollow  mould,  made  of  fine  porous  kaolin  and  attached  to  the 
cylinder  so  as  to  be  water-tight.  The  water  enters  between  the 
outer  shell  and  the  porous  mould,  penetrates  inwards  through 
the  porous  cylinder,  and  flows  away  through  the  opening  situated 
underneath. 

The  filtrate  is  bacteria-free  and  so  the  yield  of  the  filter  is 
small,  amounting  after  a  few  days  to  but  a  few  litres  per  day. 

The  apparatus  is  cleaned  by  boiling  and  thoroughly  heating 
the  dried  apparatus.  The  purified  filter  then  regains  its  original 
productivity. 

The  Chamberland  Filter  can  be  obtained  from  the  firm  of 
Lautenschlager,  Dramenburger  Strasze,  Berlin. 

(/)  Kieselguhr  Filters. 

The  chief  representative  of  these  filters  is  the  Berkefeld  Filter, 
which  is  constructed  on  the  same  principles  as  the  Chamberland 
Filter,  but  is  composed  of  baked  infusorial  earth  (see  Fig.  9). 
They  filter  free  from  bacteria  for  various  lengths  of  time,  as  a  rule 
several  days.  They  generally  yield  from  £  to  2  litres  per  minute 
at  a  pressure  of  i  to  2\  atmospheres.  Gradually  the  yield 
diminishes,  but  it  can  be  raised  again  to  just  the  original  amount 
by  brushing  the  cylinders  clean.  They  can  be  sterilised  by  simply 
warming  slowly  on  the  water-bath. 

The  filters  are,  as  far  as  freedom  from  bacteria  and  yield  are 
concerned,  certainly  the  best  small  filters.  With  daily  sterilisa- 
tion one  can  rely  with  tolerable  certainty  on  a  filtrate  continuously 
free  from  bacteria. 

The  price  of  a  filter  for  attaching  to  the  water-tap  in  houses 
is  from  30  to  35  shillings ;  smaller  types  from  13  to  16  shillings, 
and  as  pump  filters  from  46  to  200  shillings.  The  price  of  a  repair 
cylindrical  mould  is  43.  6d.,  of  an  army  filter  (yielding  \  litre 
per  minute)  30  shillings,  and  a  transportable  pump  £8.  The 
filters  can  be  obtained  from  the  Berkefeld  Filter  Co.,  Celle 
(Hanover). 

P.  Schmidt  has  studied  the  mechanism  of  bacterial  filtration 
with  Berkefeld  Filters.  He  finds  that  the  effective  size  of  the 
pores  in  Berkefeld  Filters  (with  Liliput  moulds)  is  probably  about 
0-5  /UL.  By  finely  grinding  Berkefeld  Filters  choked  up  with 


44  WATER   PURIFICATION 

bacteria,  it  was  shown  that  the  choking  only  takes  place  on  the 
surface  of  the  filter,  so  that  complete  cleaning  is  possible  in  the 
mechanical  way  by  reversal  of  the  water-current. 

Staphylococcus  and  organisms  of  about  that  size  never  pass 
through  the  filter,  but,  on  the  other  hand,  a  number  of  small 
bacteria  pass  through  in  measurable  amount  if  they  are  washed 


FIG.  9.     BERKEFELD  FILTER. 

along  in  the  water  in  very  large  quantities.  Schmidt  is  of  the 
opinion  that  for  the  passage  of  bacteria  through  a  filter  their  size 
is  of  primary  importance,  and  their  mobility  next  in  importance. 
In  general,  according  to  Konig,  the  capacity  of  a  domestic 
filter  to  retain  bacteria  depends :  (i)  on  the  nature  of  the  filtering 
medium  ;  it  must  be  uniform,  with  the  pores  not  too  big  ;  (2)  on 
the  water-pressure  ;  this  should  not  be  more  than  i  to  2  atmo- 
spheres, and  should  not  act  jerkily,  since  such  pressure  assists 


BOILING   THE   WATER  45 

the  passage  of  bacteria  through  the  filter  ;  (3)  on  the  amount  of 
pollution  in  the  water  ;  the  more  suspended  matter  a  water 
contains,  the  more  quickly  does  the  filtrate  cease  to  be  free 
from  bacteria  ;  high  temperature  also  assists  the  passage  of 
bacteria. 

Generally  speaking,  the  more  germ-tight  a  filter  is,  the  less 
productive  it  is  also. 

(ii)  Boiling  the  Water. 

All  vegetative  forms  of  bacteria  are  killed  by  long-continued 
heating  of  water  at  the  boiling-point.  Those  bacteria  which  form 
endogenous  spores  withstand,  of  course,  for  the  most  part,  the 
process  of  boiling,  but  even  they  are  considerably  weakened. 

The  pathogenic  varieties  coming  mainly  into  consideration — 
cholera  and  typhoid — form  no  endogenous  spores.  For  this 
reason  boiling  has  been  employed  with  advantage  for  the  sterilisa- 
tion of  drinking-waters  on  a  small  scale. 

If  larger  quantities  of  water  have  to  be  boiled — for  families, 
hospitals,  schools,  factories,  ships,  etc. — and  if  this  sterilisation, 
as  for  example  in  times  of  epidemic,  has  to  be  undertaken  for 
a  long  time,  then  the  following  apparatus,  according  to  von 
Esmarch,  are  to  be  recommended  :— 

(a)  The  apparatus  of  the  German  Continental  Co.  (Deutschen 
Continentalgesellschaft),     of    Dessau,     for    gas-heating,     yields 
6|  gallons  per  hour,  using  10-5  cubic  feet  of  gas  (price  £3  155.  od.). 

(b)  An  apparatus  by  Grove,  Friedrichstrasze,  Berlin,  also  for 
heating  by  gas  an  attachment  to  the  water-pipe.    This  apparatus 
yields  15  to  22  gallons  per  hour  with  14  cubic  feet  consumption 
of  gas  (price  £15) .    The  water  flowing  out  is  about  5°  warmer  than 
that  flowing  in. 

(c)  Apparatus  by  Siemens  and  Co.,  Berlin,  yields  about  8  gallons 
of  water  hourly  ;   100  gallons  require  80  cubic  feet  of  gas.     The 
price  is  £2  5s.  od.,  or,  with  a  control  apparatus  which  is  to  be 
recommended,  £3  155.  od.     The  effluent  water  is  from  5  to  10° 
warmer  than  the  inflow. 

(d)  Apparatus  by  Schaffer  and  Walcker,  Berlin,  for  gas-heating, 
yielding  6  to  8  gallons  per  hour. 

(e)  Apparatus  of  Pape  and  Henneberg,  Hamburg,  for  burning 
gas,   petroleum,   or  coal  with  automatic  self-regulation  of  the 
inflow.    The  smaller  apparatus  yields  55  gallons  hourly,  and  costs 


46 


WATER   PURIFICATION 


£38;  220  gallons  of  water  require  about  300  cubic  feet  of  gas,  or 
28  Ib.  of  coal. 

(/)  Apparatus  by  C.  Aug.  Schmidt  and  Sons,  Hamburg-Uhlen- 
horst.  The  firm  supplies  apparatus  for  houses,  hospitals,  etc., 
also  with  automatic  self-regulation  of  the  inflow.  For  a  yield 
of  20  to  30  gallons  per  hour  the  apparatus  costs  £37  to  £60 
(see  Fig.  10). 


FIG.  10.     APPARATUS  FOR  BOILING  WATER  OF  THE  FIRM  OF 
AUG.  SCHMIDT  AND  SONS,  HAMBURG-UHLENHORST. 

(g)  Transportable  apparatus  of  Rietschel  and  Henneberg, 
Berlin,  for  the  use  of  armies  and  in  case  of  epidemics.  The  plant 
yields  about  66  gallons  per  hour ;  smaller  portable  apparatus 
can  be  had,  yielding  20  gallons  per  hour. 

As  against  filtration,  purification  of  drinking-water  by  boiling 
has  the  following  disadvantages  :— 

(i)  It  only  kills  the  bacteria,  and  does  not  remove  the  suspended 
matter. 


SMALL   OZONE   PLANTS  47 

(2)  The  upkeep  of  the  apparatus  is  expensive. 

(3)  As  a  result  of  loss  of  gases  and  salts,  and  as  a  consequence 
of  the  rise  in  temperature,  boiled  water  is  generally  much  less 
palatable  than  filtered  water. 

As  opposed  to  these  disadvantages  there  are  the  following 
points  of  preference  :— 

(1)  The  productivity  remains  continuously  the  same,  whilst 
with  filters  it  falls  away. 

(2)  Boiling  the  water  renders  the  destruction  of  disease  germs 
absolutely  certain.     It  is,  on  this  account,  the  best  of  water- 
purification  methods  in  this  direction. 

(iii)  Small  Ozone  Plants  and  Ultra-Violet  Light  Apparatus. 

The  ozone  method  of  sterilising  drinking-water,  as  set  forth 
previously,  has  proved  itself  good  in  central  water  supplies. 
Lately,  various  firms,  especially  the  firm  of  Siemens  and  Halske, 
have  constructed  small  ozone  plants  for  sterilising  smaller 
quantities  of  water  for  communal  and  private  industrial  concerns, 
as  well  as  for  the  ptirpose  of  supplying  drinking-water  to  troops 
in  the  field. 

Both  stationary  and  transportable  small  ozone  plants  have 
been  designed. 

They  are  used  in  the  Munich  Brewery,  for  the  purification  of 
the  water  used  for  cleansing  vessels  and  for  similar  purposes. 
Transportable  ozone  plants  are  employed  for  the  supply  of  water 
to  troops  in  the  field.  Such  plants  were  used  by  the  Russian 
authorities  in  the  Russo-Japanese  war,  and  their  use  for  military 
purposes  is  said  to  be  under  consideration  by  various  other 
Governments.  The  whole  apparatus  is  lodged  on  two  waggons, 
the  machine-waggon  and  the  sterilisation-waggon. 

In  practice  the  raw  water  is  brought,  by  means  of  a  water-pump 
on  the  machine-waggon,  through  a  thick  suction  and  pressure  pipe 
to  a  filter,  and  from  there  to  the  sterilising-tower.  The  filter  and 
tower  are  on  the  sterilising-waggon.  Through  a  thinner  air- 
suction  and  pressure  pipe  the  air  passes  from  bellows  on  the 
machine-waggon  into  the  ozone  apparatus  on  the  sterilising- 
waggon,  and  from  here  passes  to  the  base  of  the  sterilising-tower. 
By  means  of  a  cable  the  primary  current  of  an  alternating-current 
machine  on  the  machine-waggon  is  conducted  to  the  transformer 


48  WATER   PURIFICATION 

on  the  sterilising-waggon,  which  is  set  up  directly  underneath  the 
ozone  apparatus  to  generate  the  requisite  working-tension. 

Each  waggon  requires  one  horse, and  weighs  about  i  ton. 

The  plant  yields  400  to  600  gallons  per  hour,  and  requires  for 
the  process  about  2  horse-power. 

For  safety  the  ozone  is  generated  in  such  excess  that  with 
very  dirty  water  only  one-third  to  one-half  is  consumed. 

The  apparatus  was  tested  by  Proskauer,  the  Russian  hygienist 
and  bacteriologist,  K.  Kressling,  and  a  Russian  military  com- 
mission prior  to  its  despatch  to  the  seat  of  war  in  Manchuria.  The 
results  of  these  tests  were  very  satisfactory. 

M.  Neiszer  made  a  report  on  experiments  with  two  ozone 
plants  for  work  on  a  small  scale,  which  were  placed  at  his  disposal 
by  the  firm  of  Felten  and  Guilleaume-Lahermeyer-werken  A.G. 
of  Frankfort-on-Maine. 

In  both  apparatus  the  ozone  was  generated  by  current 
from  the  supply  for  lighting  purposes.  The  mixing  of  the  ozone 
with  the  water  was  effected  by  means  of  an  aspirator  attached 
to  the  water-tap. 

Opening  the  water-tap  started  both  the  generation  of  ozone 
and  its  mixing  with  the  water.  The  ozone  generator  consists 
of  a  120  to  5000  volt  high-tension  transformer  enclosed  in  a 
protecting  box,  with  plate  condensers.  The  ozone  generator 
is  attached  to  the  town  supply  (120  volts,  45  periods)  and  con- 
sumes 0-55  ampere.  The  amount  of  ozone  generated  is  about 
5  to  6  milligrams  per  litre  of  air,  with  about  2  litres  per  minute. 
The  experiments  were  conducted  with  staphylococcus  (Staph. 
pyog.  Aur.)  and  with  bacterium  coli.  They  showed  that  with 
suitable  water  (no  suspended  matter,  no  iron,  and  little  organic 
matter),  thousands  of  bacteria  per  cubic  centimetre  can  be  killed 
with  certainty,  provided  they  have  a  resistibility  intermediate 
to  that  of  staphylococcus  and  bacterium  coli.  It  is  important  to 
observe  that  when, mixing  was  intimate,  and  when  sufficient 
quantity  of  ozone  was  used,  momentary  contact  was  sufficient 
to  kill  the  germs. 

Further,  the  firm  of  Siemens  and  Halske  have  designed,  as  a 
result  of  their  previous  experience,  a  sterilising  apparatus,  making- 
use  of  ultra-violet  light  rays,  for  affixing  to  the  domestic  supply 
and  also  for  single  water-supplies.  Their  contrivance  is  character- 
ised essentially  by  a  mechanism  whereby,  on  turning  a  single 


REMOVAL   OF   IRON   FROM    WELLS  49 

handle,  the  lamp  is  set  working  through  being  tilted,  and  at  the 
same  time  the  water-tap  is  opened.  An  electro-magnet  is 'further 
provided  which  only  allows  a  flow  of  water  through  the  apparatus 
when  the  lamp  is  properly  alight.  Also,  if  the  lamp  goes  out 
during  the  process  the  water-inflow  tap  immediately  closes,  so 
that  water  which  has  not  been  sterilised  cannot  be  drawn  from 
the  apparatus. 

(iv)  The  Removal  of  Iron  from  Single  Wells. 

The  methods  of  iron  removal,  using  small  plants,  whether  it 
be  for  the  purposes  of  a  central  water  supply  or  for  industrial 
application,  have  already  been  discussed  on  page  32  and 
the  following  pages.  There  remain  still  to  be  mentioned 
those  methods  which  serve  especially  to  remove  iron  from 
single  wells. 

The  oldest  and  simplest  method  of  removing  iron  from  well- 
water  is  to  pour  into  the  well  iron-free  water  which  has  taken  up 
oxygen  (generally  by  standing  in  the  air).  The  oxygen  precipi- 
tates the  iron  as  hydroxide,  which  then  settles  to  the  bottom. 
Water  can  in  this  way  be  freed  for  many  days  from  the  iron  it 
contains.  The  chief  disadvantage  lies  in  the  fact  that  the 
precipitated  iron  remains  in  the  well.  In  addition  to  this  the 
water  poured  into  the  well  should,  of  course,  be  hygienically 
free  from  any  objection,  which  it  never  is. 

For  this  purpose  the  Dunbar  Filters  are  very  suitable.  Of  such 
filters  the  simplest  and  cheapest  construction  consists  of  a  tub 
rilled  with  sand,  having  a  tap  in  the  side  at  the  bottom.  The 
water  is  allowed  to  flow  out  of  the  pump  on  to  the  sand.  The  iron- 
free  water  is  removed  through  the  tap  underneath.  About  every 
three  months  the  sand  must  be  freed  from  the  precipitated 
oxide  of  iron  by  washing.  Such  an  arrangement  is  not  suitable 
to  wells  situated  in  the  open,  since  they  are  liable  to  freeze. 
Still,  this  objection  can  be  overcome,  as  the  whole  plant  can 
be  housed  against  the  frost  in  a  special  small  hut. 

The  Deseniss  and  Jacobi  system  of  so-called  bastard  pumps 
(see  Fig.  n)  differs  from  all  other  systems  in  this,  that  by  means 
of  a  pump  the  water  is  taken  from  the  well  already  freed  from 
iron.  All  intermediate  apparatus,  such  as  scrubbers,  clarifying 
reservoirs,  etc.,  are  therefore  not  required. 
E 


50  WATER   PURIFICATION 

The  following  is  the  arrangement  and  method  of  working  such 
pumps  :  To  the  pump  employed  for  raising  the  water  there  is 
attached  a  second  cylinder  of  double  the  circumference  of  the 
cylinder  of  the  water-pump.  In  both  cylinders  there  move 


FIG.  ii.     THE  BASTARD  PUMP 
OF  DESENISS  AND  JACOBI. 

tightly  closing  pistons,  provided  with  valves  and  fastened  to 
a  piston-rod.  The  water  streaming  in  from  the  lower  cylinder 
to  the  one  above,  since  the  latter  has  double  the  capacity  of  the 
former,  is  thus  mixed  with  an  equal  volume  of  air,  sucked  in 
through  a  valve  laterally  placed  in  the  higher  cylinder.  After 
being  mixed  with  air  the  water  is  forced  on  to  a  forged-iron  filter, 
carrying  sand  of  0-5  millimetre  grain  as  filtering  material.  It  is 
thereby  freed  from  the  hydroxide  of  iron  that  has  been  formed. 
The  filter  can  be  set  up  in  a  small  shaft  standing  in  close  proximity 
to  the  pump,  or  it  may  even  be  placed  in  the  pump  uprights 
itself. 

It  is  not  necessary  to  renew  the  filter  layer  at  all ;  the  purifica- 


PURIFICATION   FOR   TECHNICAL   PURPOSES        51 

tion  of  the  filter  is  effected  by  temporary  automatic  flooding 
in  the  reverse  direction,  and  is  attained  by  simply  reversing  the 
stop-cocks. 

Schreiber  has  tested  this  method  in  an  experimental  plant,  set 
up  in  the  chief  pumping-station  of  the  Charlottenburg  ground- 
water  works.  He  finds  that  the  pump  removes  even  the  last 
traces  of  iron,  or  at  most  leaves  an  inconsiderable  amount  behind. 
It  further  fulfils  all  the  demands  made  upon  a  hand-pump  as 
regards  simplicity  in  construction,  slight  supervision,  and  pro- 
tection against  pollution. 

Moreover,  the  bastard  pump  is  not  only  supplied  for  hand- 
work, but  also  for  working  by  machinery. 

According  to  the  declarations  of  the  firm,  the  removal  of  the 
iron  should  be  alike  complete  with  a  hand-pump  of  usual  size, 
or  with  a  large-scale  plant  yielding  many  thousands  of  litres  per 
hour. 

B.    Purification  of  Water  for  Technical  Purposes. 

Besides  the  use  of  natural  water  for  drinking  purposes,  water 
is  needed  for  almost  all  human  occupations.  In  most  cases  with 
a  natural  water  purification  is  not  necessary  for  technical  pur- 
poses, since  the  demands  made  upon  the  quality  of  such  a  water 
are  naturally  less  than  with  a  drinking-water. 

For  cleansing  public  urinals  and  lavatories,  for  fountains,  and 
for  watering  the  streets  and  gardens,  untreated  river-water  is 
frequently  used.  Where  the  river-water  is  very  dirty,  at  most 
a  coarse  gravel  filter  is  employed,  and  this  simply  serves  to  retain 
suspended  matter,  but  not,  as  is  the  case  with  drinking-water, 
the  bacteria.  Many  towns,  like  Frankfort-on-Maine,  have  along- 
side the  drinking-water  pipe,  one  for  river-water,  which  serves 
the  purposes  mentioned. 

For  many  industrial  purposes  the  water,  however,  must  undergo 
treatment.  For  example,  in  paper  manufacture,  the  presence  of 
iron  is  troublesome,  since  iron  forms  a  compound  with  cellulose 
and  makes  the  paper  spotty.  The  removal  of  iron  in  such  cases 
is  effected  in  small  iron-removal  plants,  which  have  already  been 
described  on  page  32  and  the  following  pages.  In  many  industries 
—for  example,  with  laundries,  dye  works,  and  others — hard  water 
is  a  great  disadvantage,  as  a  part  of  the  working  material  is 


52  WATER   PURIFICATION 

precipitated  by  the  constituents  causing  hardness,  and  is  thereby 
rendered  useless.  Hence,  for  such  purposes  the  water  must  be 
softened.  Quite  generally,  however,  the  softening  of  water 
plays  a  large  part  in  industry,  owing  to  the  use  of  water  in  boilers. 

The  Softening  of  Boiler-Feed  Waters. 

The  hardness  of  a  water  is  due  to  the  calcium  and  magnesium 
salts  dissolved  in  it.  A  distinction  is  drawn  between  temporary 
hardness,  or  hardness  due  to  carbonates,  and  permanent  hardness, 
or  hardness  due  to  mineral  acid  salts.  Carbonate  hardness  is 
caused  by  the  bicarbonates  of  calcium  and  magnesium  which, 
unlike  the  normal  salts,  are  soluble  in  water.  On  boiling  the  water 
these  bicarbonates  give  up  half  their  carbon  dioxide  in  the  free 
state,  change  to  the  normal  salt,  and  therefore  become  insoluble. 
The  observation  that  a  part  of  the  hardness  of  water  disappears 
on  boiling  has  earned  for  such  hardness  the  title  of  temporary 
hardness. 

Permanent  hardness  is  due  to  the  presence  of  the  salts  of  cal- 
cium and  magnesium  with  sulphuric,  hydrochloric,  and  nitric 
acids,  and  therefore  to  calcium  and  magnesium  sulphates, 
chlorides,  and  nitrates. 

Hardness  is  measured  in  German  or  French  degrees  of  hardness. 
i°  on  the  German  scale  is  equivalent  to  i  mg.  CaO  or  074  mg. 
MgO  per  100  c.cs.  of  water.  i°  on  the  French  scale  is  equivalent 
to  i  mg.  CaCO3  or  0-84  mg.  MgCO3  per  100  c.cs.  water.1 

If  hard  water  is  used  for  feeding  boilers,  in  process  of  time  there 
settles  on  the  boiler  plates  a  scale,  consisting  of  precipitated 
calcium  and  magnesium  salts.  With  a  large  amount  of  tem- 
porary hardness,  there  further  results  in  the  boiler  a  big  sludge  of 
loose,  precipitated  normal  calcium  carbonate.  The  troublesome 
effects  of  this  boiler  scale  are  well  known.  In  the  first  place,  once 
a  boiler  scale  has  reached  a  certain  thickness,  the  conductance  of 
heat  to  the  water  is  greatly  hindered,  and  so  coal  is  consumed 
very  uneconomically.  Boiler  scale  can  also  lead,  however,  to 
the  direct  deterioration  of  the  boiler  plates,  since  the  scale 
possesses  a  different  coefficient  of  expansion  from  that  of  the 
boiler  plates.  In  this  way  fissures  and  cracks  result.  The 
chlorides  of  lime  and  magnesium,  when  present  in  water  in  fairly 

1   i°  on  the  English  scale  is  equivalent  to  i  grain  CaCO3  per  gallon.  —  Trans. 


PURIFICATION   FOR   TECHNICAL   PURPOSES        53 

large  amounts,  are  very  troublesome  as  they  are  hydrolysed 
with  formation  of  free  hydrochloric  acid,  which  passes  away  with 
the  steam  and  attacks  the  equipment. 

At  the  present  time  three  methods  are  principally  employed 
for  softening  water,  namely,  the  Lime-soda  method,  the  Reisert 
Baryta  process,  and  the  Permutit  process. 

The  lime-soda  method,  as  the  name  implies,  consists  in  adding 
to  the  water  lime  and  sodium  carbonate.  The  temporary  hard- 
ness is  removed,  by  the  addition  of  lime,  in  the  form  of  calcium 
carbonate  and  magnesium  hydroxide,  according  to  the  following 
equations  :— 

1.  Ca(HC03)o  +  Ca(OH)2=2  CaCO3+2  H2O. 

2.  (a)  Mg(HC03)2+Ca(OH)2  =  CaC03+MgC03+2H20. 
(b)  MgC03+Ca(OH)2=Mg(OH)2+CaC03. 

Permanent  hardness  is  removed  by  means  of  sodium  carbonate 
according  to  the  following  equations  :  — 

1.  CaS04  +Na2C03  =CaCO3  +Na2SO4. 

2.  (a)  MgCl2  +Na2C03  =MgCO8+2NaCL 

(b)   MgC03  +  Ca(OH)2=CaC03  +Mg(OH)2  (Pfeiffer). 


All  calcium  salts  in  the  water  are  therefore  precipitated  in  the 
form  of  the  normal  carbonate  ;  all  magnesium  salts,  no  matter 
in  what  form  they  are  present  (whether  as  temporary  or  per- 
manent hardness),  are  finally  precipitated  as  the  completely 
insoluble  hydroxide.  Hardness  due  to  carbonates  is  therefore 
entirely  removed  from  water  by  this  method,  but  in  place  of  the 
precipitated  salts  causing  permanent  hardness,  an  amount  of 
sodium  equivalent  to  the  calcium  and  magnesium  originally 
present  passes  into  the  water  as  sulphate,  chloride,  or  nitrate. 

From  the  equations  given  it  can  easily  be  calculated  that,  for 
each  degree  of  temporary  hardness,  10  g.  of  lime  (100%  CaO)  are 
needed  to  soften  i  cubic  metre  of  water.  Also  it  is  obvious  from 
the  equation  that  for  each  milligramme  of  magnesia  present 
in  a  litre  of  water,  no  matter  what  the  form,  1-4  g.  of  lime  (100% 
CaO)  must  be  added  to  a  cubic  metre  of  the  water.  For  each 
degree  of  permanent  hardness  19  g.  of  sodium  carbonate  (100% 
Na2CO3)  are  needed  per  cubic  metre.  In  the  measurement  of  the 
quantity  added,  it  is  to  be  borne  in  mind  that  natural  waters 
generally  contain  some  free  carbon  dioxide.  Since  carbonic  acid 


54  WATER   PURIFICATION 

combines  with  lime  to  form  bicarbonate,  which  then,  of  course, 
combines  with  more  lime  to  form  the  normal  carbonate,  for  every 
milligram  of  free  carbon  dioxide  per  litre  an  addition  of  1-27  g. 
of  100%  CaO  must  be  made  per  cubic  metre,  in  order  to  neutralise 
this  free  carbonic  acid.  The  addition  of  lime,  therefore,  must  be 
increased  by  such  an  amount  for  every  milligram  of  free  carbon 
dioxide  present. 

From  various  investigations,  however,  the  amount  of  lime  to 
be  added,  thus  theoretically  reckoned,  proves  to  be  too  high  in 
practice.  It  must  be  cut  down  by  about  20  to  25  per  cent.  Vari- 
ous reasons  for  this  have  been  put  forward. 

Instead  of  calcium  hydrate,  caustic  soda  can  be  used.  From 
the  bicarbonate  there  results  sodium  carbonate  which,  in  its 
turn,  serves  to  remove  permanent  hardness. 

Ca(HCO3)2+2  NaOH  =  CaCO3+Na2CO3+2  H2O. 
Mg(HCO3)  2  +4  NaOH  =Mg(OH)  2  +2  Na2CO3  +2  H2O. 


If  precisely  so  much  temporary  hardness  is  present  that  the 
sodium  carbonate  resulting  according  to  the  above  equations 
is  just  sufficient  to  remove  the  permanent  hardness,  then  the 
water  can  be  completely  softened  with  sodium  hydrate.  If 
more  permanent  hardness  is  present,  then  the  sodium  carbonate 
still  required  has  to  be  added.  If,  on  the  other  hand,  there  is  too 
little  permanent  hardness,  only  so  much  sodium  hydrate  should 
be  added  as  can  form  the  amount  of  sodium  carbonate  requisite 
for  the  removal  of  the  permanent  hardness.  The  remainder  of 
the  unprecipitated  carbonates  must  then  be  removed  by  means 
of  lime. 

Formulae  for  reckoning  the  necessary  addition  of  caustic  soda, 
sodium  carbonate,  and  lime  have  frequently  been  given.  If  a 
is  the  combined  carbonic  acid,  b  the  total  lime,  and  c  the  total 
hardness  expressed  in  equivalents  of  hardness,  then  the  following 
formulae  of  Kalmann  give  the  necessary  additions  of  caustic 
soda,  lime,  and  sodium  carbonate  :— 

m=2a  —  b  ;  n=c—a. 

If  m  and  n  are  positive,  the  water  contains  more  temporary 
than  permanent  hardness  ;  m  is  then  the  lime  to  be  added,  n  the 
caustic  soda. 

If  2a  —  b=o,  there  is  present  in  the  water  as  much  temporary 


PURIFICATION   FOR   TECHNICAL   PURPOSES        55 

as  permanent  hardness.  No  lime  is  then  needed,  but  only  n  units 
of  caustic  soda. 

If  2a  —  b  is  negative,  the  water  contains  rnore  permanent  than 
temporary  hardness.  There  must  then  be  added  m  parts  of 
sodium  carbonate  and  c—a=n  parts  of  caustic  soda  (Wehren- 
pf  ennig) . 

The  caustic  soda  is  generally  prepared  by  mixing  sodium 
carbonate  solution  with  lime  and  allowing  the  precipitated 
calcium  carbonate  to  settle. 

In  ascertaining  the  necessary  addition,  if  lime  and  sodium 
carbonate  be  reckoned,  and  not  caustic  soda,  precisely  the  same 
amounts  require  to  be  added  as  were  given  above,  on  page  53, 
for  lime  and  sodium  carbonate.  Therefore,  with  caustic  soda 
as  the  softening  agent,  the  numbers  given  with  respect  to  lime 
and  sodium  carbonate  can  be  adhered  to. 

The  lime-soda  process  is  the  oldest,  and  doubtless,  also,  has 
the  widest  practical  application  at  the  present  time.  Softening 
with  lime  and  sodium  carbonate  never  attains  o°  hardness,  but 
generally  only  about  3°  to  4°,  which,  however,  is  quite  sufficient 
for  general  requirements.  There  are  numerous  firms  who  construct 
softening  plants  of  the  lime-soda  type,  which  are  used  with  the 
greatest  success  in  practice.  Among  others  are  the  firm  of 
Humboldt  in  Kalk,  Dehne  in  Halle  a,  S.,  Reisert  in  Cologne,  and 
the  "  Voran  "  firm  of  Frankfort-on-Maine.  Figure  12  represents 
a  lime-soda  softening  plant,  "  Voran  "  system. 

This  plant  may  be  briefly  described  as  an  example  of  a  lime-soda 
softener. 

The  automatic  water-purification  apparatus  of  the  "  Voran  " 
System  (Model  BI)  consists  essentially  of  reservoir  A,  divided  into 
three  parts  by  means  of  partition-walls,  the  clarifying  tank  B, 
the  lime  saturator  C,  the  sodium  carbonate  regulator  D,  and  the 
filter  of  wood  shavings  and  wood-wool  arranged  under  the 
clarifying  tank  B. 

The  raw  water  which  is  led  into  the  apparatus  through  the 
pipe  E  next  flows  through  the  discharge  pipe  F  into  the  part  of 
the  tank  A  set  aside  for  the  raw  water. 

In  this  section,  at  equal  heights,  are  placed  two  stop-cocks 
G  and  H,  through  which  the  raw  water  can  flow  away.  The 
larger  portion  goes,  through  the  stop-cock  G  and  the  pipe  G1} 
directly  to  the  funnel-shaped  central  portion  I,  in  which  it 


56 


WATER  PURIFICATION 


takes   up   a  violent   whirling  motion   owing   to   its    tangential 
entry. 

The  smaller  quantity  of  raw  water,  arranged  exactly  according 
to  the  amount  of  lime-water  required,  flows  through  the  stop- 
cock H  and  the  discharge  tube  Hx  to  the  lime  saturator  C,  to  the 


Raw   Wa 
Inflow. 


FIG.  12.     LIME-SODA  WATER  SOFTENER.     "  VORAN  "  SYSTEM. 

bottom  of  which  it  is  led  through  the  central  funnel-pipe  H2  in 
order  that  it  may  pass  into  the  saturator  equally  distributed  on 
all  sides. 

From  here  on  its  way  to  the  overflow  K  the  raw  water  is  com- 
pelled to  percolate  through  the  milk  of  lime  which,  since  it  is 
specifically  heavier  than  water,  has  settled  to  the  bottom.  The 


PURIFICATION   FOR  TECHNICAL   PURPOSES        57 

water  is  thereby  itself  completely  saturated  with  caustic  lime 
and  flows  away  at  the  top  completely  saturated  and  clear  lime- 
water,  through  the  overflow-pipe  K  to  the  mixing-trough. 

If  the  ratio  of  clear  saturated  lime-water  to  raw  water  is  once 
fixed,  then  it  will  always  remain  the  same,  whether  much  or  little 
raw  water  is  flowing  in,  for  the  amounts  of  raw  water  flowing 
through  the  two  stop-cocks  G  and  H  should  always  be  pro- 
portional. 

The  soda  solution  necessary  flows  from  its  particular  part  of 
the  reservoir  A  through  a  hair-sieve  M  and  the  attached  pipe  MT 
to  the  sodium  carbonate  regulator  D,  in  which  the  inflow  is 
regulated  by  the  float  N.  From  the  regulator  D  the  sodium 
carbonate  solution  passes  to  the  mixing-trough  through  the 
exit  pipe  Q,  so  arranged  that  it  can  be  revolved,  and  which  is 
attached  in  its  turn  to  the  float  R  in  the  raw-water  reservoir. 
When  the  float  R  sinks  the  discharge-pipe  Q  is  raised  and  the 
discharge  reversed. 

If  the  raw-water  section  of  the  reservoir  becomes  empty  at 
any  time,  the  float  R  will  sink  to  the  bottom,  thereby  raising  the 
discharge-pipe  so  high  that  no  more  sodium  carbonate  can  flow 
out. 

On  the  other  hand,  the  three  streams  of  raw  water,  lime-water, 
and  sodium  carbonate  solution  commence  to  flow  simultaneously, 
as  soon  as  raw  water  flows  into  its  particular  section  of  the 
reservoir. 

By  this  means  the  amount  of  chemicals  added  always  bears  a 
fixed  ratio  to  the  amount  of  raw  water  consumed,  that  is  to  say, 
the  apparatus  is  automatically  self-regulating. 

If  too  much  raw  water  be  led  into  the  raw- water  reservoir  it  is 
run  off  by  means  of  an  overflow-pipe. 

The  lime-water  and  sodium  carbonate  solution,  after  mixing, 
flow  from  the  mixing-trough  to  the  central  funnel-shaped  pipe 
I,  and  of  course  meet  the  circular  motion  of  the  raw  water  there. 
In  this  way  an  intimate  mixing  with  the  water  is  ensured,  and 
the  commencement  of  the  reaction  is  hastened.  It  is  especially 
advantageous  for  the  rapid  progress  of  the  reaction  to  have  the 
cross  section  of  the  pipe  I  wide  at  the  top  and  decreasing  down- 
wards, since  with  a  constantly  increasing  velocity  of  water  a 
stronger  whirling  motion  is  produced  and  a  more  intimate  mixing 
ensues. 


58  WATER   PURIFICATION 

After  leaving  I  the  water  is  reversed  in  direction  and  then 
distributed  uniformly  in  the  reaction  space  and  clarifying  portion 
B.  Owing  to  the  comparatively  large  cross  section  of  the  chamber 
the  water  rises  to  the  top  with  very  slow  velocity,  and  on  this 
account  is  freed  as  far  as  possible  from  fine  suspended  matter. 

The  greater  part  of  the  sludge  does  not  alter  its  direction  with 
the  water,  but  in  consequence  of  its  higher  specific  gravity  sinks 
to  the  bottom.  It  settles  there  in  the  sludge  tank  T,  from  which 
it  can  be  withdrawn  as  required  through  the  stop-cock  T. 

The  water  rising  to  the  top  of  the  clarifying  space  B,  by  the 
time  it  has  reached  the  discharge-pipe  U,  has  allowed  the  greater 
part  of  the  insoluble  precipitated  components  to  settle  out. 

Consequently  through  the  discharge-pipe  M,  water  carrying 
only  floating  particles  passes  to  the  underneath  side  of  the  filter. 
These  remaining  particles  are  retained  during  the  passage  of  the 
water  through  the  filter,  with  the  result  that  the  water  leaves 
the  apparatus  at  l^  softened  and  filtered,  to  be  led  away  to  the 
place  of  consumption. 

The  wood-shaving  or  wood-wool  filter  will  only  need  cleaning 
or  renewing  at  long  intervals  of  time,  perhaps  after  six  to  twelve 
months,  since  it  is  only  very  slightly  used.  Renewal  should 
easily  be  effected  at  a  cost  of  a  few  shillings. 

The  disadvantage  of  the  lime-soda  process  is  simply  this,  that 
in  place  of  permanent  hardness,  as  has  been  already  mentioned, 
an  equivalent  amount  of  sodium  salts  passes  into  solution. 
These  sodium  salts  are,  of  course,  quite  neutral  and  readily 
soluble  in  water,  but  in  course  of  time  attain  to  such  a  strong 
concentration  in  the  boiler  that  they  cause  inconvenience.  The 
salts  crystallise  at  the  valves,  irregular  boiling  of  the  water 
occurs,  and  so  on.  The  lye  must  then  be  blown  off.  A  further 
disadvantage  of  the  process  is  this,  that  with  the  addition  of  too 
much  lime  and  sodium  carbonate  the  boiler  plates  may  be 
attacked.  Generally,  however,  with  frequent  checking  of  the 
pure  water  produced,  the  process  can  be  worked  in  such  a  way 
that  just  the  right  amount  of  substances  is  added.  Blacher 
rightly  calls  attention  to  the  fact  that  it  is  not  sufficient  to  control 
only  the  softened  water,  but  that  the  control  must  extend  also 
to  the  water  in  the  boiler.  For,  even  if  only  a  slight  excess  of 
the  reagents  be  present,  these  excesses  are  concentrated  in  the 
boiler  in  such  a  way  that  the  boiler  plates  will  be  attacked. 


PURIFICATION   FOR   TECHNICAL   PURPOSES        59 

According  to  Blacher  it  is  considered  permissible  for  the  water 
to  contain  up  to  3°  of  permanent  hardness  and  excess  of  sodium 
carbonate  up  to  57  milligrams  Na2CO3  per  litre. 

The  Reisert  Baryta  process  for  softening  water  removes 
temporary  hardness  by  means  of  lime  exactly  as  in  the  first  • 
named  process.  The  most  troublesome  permanent  hardness  in 
boiler-water  is  due  to  gypsum,  as  this  yields  hard  boiler  scale, 
which  adheres  very  tenaciously  to  the  boiler  plates.  The  Reisert 
method  is  therefore  confined  to  the  removal  of  that  permanent 
hardness  due  to  gypsum,  and  this  is  effected,  of  course,  by  the 
addition  of  barium  carbonate.  Barium  carbonate  is  practically 
insoluble  in  water.  It  is  deposited  in  the  water,  care  being  taken 
that  it  remains  in  contact  with  the  water  for  a  period  of  time, 
during  which  the  following  decomposition  with  the  calcium 
sulphate  takes  place  : — 

CaSO4 + BaCO3 = BaSO4 + CaCO3. 

Gypsum  and  barium  carbonate  are  therefore  converted  into 
insoluble  calcium  carbonate  and  completely  insoluble  barium 
sulphate.  The  lime  necessary  is  naturally  the  same  as  in  the 
lime-soda  process,  no  matter  what  the  amount  of  barium  car- 
bonate is.  Also,  the  whole  of  the  magnesia  is  finally  precipitated 
as  hydroxide,  so  that  it  holds  in  this  case  also  that  each  milli- 
gramme of  MgO  present  in  the  water  requires  double  the  amount 
of  lime.  Therefore,  for  each  milligramme  of  MgO  per  litre  the 
amount  of  lime  to  be  added  per  cubic  metre  must  be  raised  to 
1-4  grammes  of  100  per  cent  CaO,  according  to  the  methods  of 
estimation  on  the  basis  of  hardness  discussed  previously. 

The  chief  point  of  preference  in  the  baryta  process  lies  in  the 
fact  that  the  sodium  carbonate,  which  when  present  in  con- 
siderable excess  in  the  softened  water  acts  very  corrosively  on 
the  equipment,  is  done  away  with.  Since  barium  carbonate  as 
mentioned  is  practically  insoluble  in  water,  the  baryta  process 
possesses  the  further  advantage  that  the  addition  of  carbonate 
may  be  liberal.  An  excess  of  barium  carbonate  is  thrown  into  the 
water,  which  is  then  allowed  after  a  certain  time  to  settle  free 
from  the  undissolved  matter,  whereupon  it  can  be  employed 
immediately.  An  excess  of  barium  carbonate  is  impossible  in 
the  water  softened.  Further,  in  the  baryta  process,  another 
inconvenience  mentioned  in  the  lime-soda  process  disappears. 


60  WATER   PURIFICATION 

In  that  process  in  place  of  the  permanent  hardness  sodium 
salts  enter  the  water.  By  the  baryta  method  the  temporary 
hardness  and  that  due  to  calcium  sulphate  is  removed  practically 
quantitatively.  It  can  therefore  be  said  of  this  process  that  there 
is  less  risk  of  corrosion  in  the  boiler  than  is  the  case  with  the 
lime-soda  process. 

Against  these  advantages  of  the  baryta  process  there  stand  a 
number  of  disadvantages.  Only  sulphate  hardness  and  not  that 
of  chlorides  or  nitrates  is  removed  with  barium  carbonate.  It 
is  consequently  only  applicable  to  water  which  does  not  contain 
these  salts  in  appreciable  amounts.  Waters  containing  alkali 
sulphates  cannot  be  softened  by  the  baryta  process,  since  in  this 
case  sodium  carbonate  would  be  formed  by  the  interaction  of  the 
barium  carbonate  with  the  alkali  sulphates,  according  to  the 
following  equation  : 

Na2SO4 + BaCO3 = Na2CO3 + BaSO4. 

Sodium  carbonate  would  therefore  be  present  in  the  softeaed 
water,  would  get  into  the  boiler  and  ruin  it. 

The  most  recent  method  used  in  practice  is  the  Permutit 
method.  Permutit  is  a  complex  compound  of  sodium,  aluminium, 
and  silicic  acid.  Such  compounds  occur  in  nature  as  zeoliths. 
Permutit  is  the  name  for  the  artificial  product  obtained  by 
melting  aluminium  silicate  with  sodium  carbonate,  and  has 
the  peculiar  property  of  removing  lime,  magnesia,  manganese, 
or  iron  from  water  when  such  water  is  slowly  filtered  over  it. 
At  the  same  time  equivalent  amounts  of  sodium  are  given  up  to 
the  water.  The  process  would  scarcely  have  come  into  practical 
consideration  at  all  if  it  had  not  been  discovered  simultaneously 
that  permutit  or  zeolith,  through  which  water  has  been  filtered 
for  a  long  time,  and  which  has  quite  lost  its  softening  capacity, 
can  be  easily  regenerated  by  washing  it  with  a  solution  of  common 
salt.  Thus  the  process  can  be  reversed.  The  bases  removed 
pass  back  into  solution,  and  in  their  stead  sodium  from  the 
common  salt  passes  into  the  compound.  The  product  so  washed 
is  precisely  of  the  same  utility  as  the  original,  and  after  working 
itself  out  again  can  be  regenerated  anew. 

The  advantages  of  the  process  are  manifest.  Above  all,  the 
process  is  extraordinarily  simple  to  manage.  It  is  simply  a 
question  of  filtering  the  water  to  be  softened  through  a  layer  of 


PURIFICATION   FOR   TECHNICAL   PURPOSES        61 

permutit  of  a  certain  depth  at  a  velocity  determined  by  tests. 
Unlike  the  two  softening  processes  previously  mentioned,  which 
both  reduce  the  hardness  only  to  about  3  to  4°,  with  methodical 
control  the  softening  in  this  process  readily  reaches  o°.  A  further 
advantage  is  naturally  that  the  necessity  for  the  addition  of 
definite  amounts  of  reagent  is  obviated.  The  main  disadvantage 
of  the  process  lies  in  the  fact  that  with  water  rich  in  carbonates 
(and  most  hard  waters  are  rich  in  these  salts),  in  place  of  the 
substances  removed  an  equivalent  amount  of  sodium  bicarbonate 
enters.  In  the  boiler  the  sodium  bicarbonate  gives  up  half  its 
carbon  dioxide  and  is  converted  to  the  normal  salt.  There  will 
therefore  be  constantly  present  in  the  boiler  water  containing 
sodium  carbonate  which  may  cause  corrosion  as  already  men- 
tioned. 

The  method  is  employed,  as  previously  noted,  not  only  for 
softening,  but  also,  especially  of  late  years,  for  removing  iron 
and  manganese  from  waters. 

Softening  plants  of  the  Permutit  type  are  supplied  by  the 
Permutit  Filter  Co.,  Berlin. 

For  the  correct  working  of  a  softening  plant,  expert  super- 
vision, by  examination  of  both  the  softened  and  the  boiler  water, 
is  of  the  utmost  importance.  Blacher  a  short  time  ago  suggested 
a  very  subtle  method,  by  the  aid  of  which  exact  insight  can  be 
obtained  into  the  existing  conditions  in  boiler  management. 
The  method  consists  in  finding  out  the  acid  required  to  neutralise 
the  boiler  water  by  titration  with  r<s  acid,  first  using  phenol 
phthalein  and  then  methyl-orange  as  indicator.  In  addition  the 
total  hardness  is  estimated  with  potassium  stearate  and  phenol 
phthalein.  From  these  three  values,  which  can  be  obtained  in 
quite  a  short  time,  one  is  in  a  position  to  suggest  how  the  water 
is  constituted.  Professor  Blacher  has  constructed  a  box  for 
testing  raw  water,  softened  water,  and  boiler-water,  which  with 
the  accompanying  instructions  can  be  obtained  at  a  cost  of 
25  shillings  from  the  Vereinigten  Chemischen  Fabriken  fur 
Laboratoriumsbedarf  of  Berlin.  Every  boiler  user  is  warmly 
recommended  to  provide  himself  with  one.  The  necessary  experi- 
mental work  can  be  learned  by  an  intelligent  foreman. 

In  conclusion  it  may  further  be  pointed  out  that  the  so-called 
boiler-scale  preventatives  which  are  often  recommended  are 
very  much  advertised  and  overrated.  In  the  majority  of  cases 


62  WATER   PURIFICATION 

they  are  crude  swindles,  for  it  is  self-evident  that  substances  like 
sugar,  starch,  and  others  are  not  such  as  would  prevent  boiler 
scale.  Of  late,  remedies  have  come  into  the  market  whose  action 
depends  on  simultaneous  deposition  of  the  medium  along  with 
the  boiler  scale,  whereby  the  scale  is  of  a  softer  nature  and  more 
easily  removed.  It  is  not  impossible  that  such  a  remedy  might 
actually  be  successful,  but  a  certain  amount  of  scepticism  exists 
in  regard  to  them.  The  most  rational  method  of  protecting 
oneself  against  damage  due  to  the  formation  of  boiler  scale  is 
always  a  properly  managed  softening  plant. 


SEWAGE    DISPOSAL 


THE  SIGNIFICANCE  OF  RIVER  POLLUTION  AND  THE 
IMPORTANCE    OF   SEWAGE   DISPOSAL. 

A  LL  water,  whether  for  drinking  or  domestic  purposes  generally, 
A\  or  whether  employed  in  cleansing,  washing,  and  industrial 
processes,  when  not  consumed  through  leakage,  evaporation,  or  in 
some  such  manner,  eventually  becomes  sewage.  Unlike  purified 
water,  or  even  a  natural  unpurified  surface-water,  sewage  varies 
considerably  in  composition.  It  contains  suspended  and  dis- 
solved organic  and  inorganic  matter  in  more  or  less  large  quanti- 
ties, and  on  this  account  is  characterised  by  a  muddy  appearance 
and  frequently  also  by  a  foul  odour. 

The  purification  of  sewage  is  quite  recent  in  its  origin.  Even 
up  to  a  few  decades  ago  short  work  was  made  of  effluents. 
Generally  speaking,  the  water  used  in  dwelling-houses  was 
conducted  in  ordinary  open  sewers  to  the  nearest  river. 

The  vast  increase  of  large  towns  and  the  unexpected  progress 
of  industry  led  to  the  most  serious  nuisances  in  this  disposal  of 
sewage  into  rivers.  The  evil,  which  is  every  day  becoming  more 
apparent,  is  both  hygienic  and  economic. 

Many  large  towns  are  dependent  on  river-water  for  their 
water  supply.  As  was  explained  in  the  previous  section,  the 
bacteria  are  generally  removed  by  means  of  a  sand  filter.  Apart 
from  the  consideration  that  the  filter  naturally  cannot  remove 
dissolved  filth,  substances  which  owing  to  their  origin  may  be 
harmless  seem  to  leave  a  water  unappetising  as  a  drinking-water. 
Also  a  greater  pollution  of  surface-water  with  sewage  produces  a 
larger  number  of  bacteria  in  the  filtered  water,  since  no  filters 
are  completely  germ-tight.  This  is  all  the  more  serious,  as, 
naturally,  in  sewage  waters  which  contain  all  human  excreta, 
disease  germs  may  very  easily  be  present. 

In  those  places  where  surface-waters  are  not  used  for  the 

63 


64  SEWAGE   DISPOSAL 

water  supply,  river-water  is  nevertheless  often  used  for  baths, 
washing,  watering  the  streets,  and  similar  purposes.  All  these 
processes  ought  to  be  carried  out  without  any  danger  to  health. 

It  was  shown  by  the  Director  of  the  Pasteur  Institute  in 
Constantinople  that  cases  of  cholera  that  occurred  in  the  year 
1908  could  be  attributed  to  infection  of  the  hands  with  the  water 
of  the  Bosphorus  and  the  Golden  Horn.  Similarly  it  was  medi- 
cally established  with  absolute  certainty  that  a  number  of  typhoid 
cases  in  the  French  army  had  resulted  through  bathing  in 
polluted  waters. 

These  examples  show  that  river  pollution  may  be  very  serious 
both  as  regards  washing  and  bathing.  Apart,  however,  from 
these  direct  dangers  it  is  greatly  to  be  regretted  if  river  baths, 
which  in  the  view  of  experts  are  decidedly  superior  from  the 
standpoint  of  health  to  baths  in  closed  rooms,  are  avoided  as  a 
result  of  the  foul  and  unattractive  nature  of  the  water. 

Besides,  a  river  polluted  with  sewage,  choked  with  mud,  or 
even  smelling  badly,  will  excite  in  every  normal  man  feelings  of 
repugnance  and  displeasure  which  may  have  economic  results, 
for  the  banks  of  such  a  river  are  avoided  as  places  of  residence. 
Where  a  polluted  river  flows  through  or  by  a  town,  there  is 
always  a  danger  of  the  river-banks  depreciating  in  value. 

In  addition  to  the  great  economic  disadvantages  of  the  pollu- 
tion of  rivers,  harm  also  results  in  the  destruction  of  fish.  Often 
the  fish  are  ruined  in  large  quantities  by  the  introduction  of 
sewage  into  the  river.  The  delicate  and  precious  varieties 
especially  are  very  sensitive  to  pollution  of  the  water,  and  very 
soon  disappear  entirely  with  continued  pollution.  With  certain 
kinds  of  sewage  containing  substances  of  specific  taste  or  smell, 
the  fish  assume  similar  taste  and  smell.  An  embarrassing  point 
of  social  significance  relative  to  this  is,  that  lower  middle-class 
people,  like  fishermen  and  proprietors  of  baths,  the  protection 
and  maintenance  of  whom  in  these  days  of  the  capitalist  on  the 
one  hand  and  the  proletariat  on  the  other  seems  to  be  demanded, 
are  either  annihilated  or  grievously  injured  economically.  A 
disadvantage  too  of  river  pollution,  by  no  means  insignificant 
economically,  is  demonstrated  also  in  this,  that  as  a  result  of  the 
deposition  of  mud  on  the  river-bed,  expenditure  has  to  be  in- 
curred in  dredging  operations  to  remove  the  mud  and  in  similar 
processes  of  purification. 


RIVER    POLLUTION  65 

Consequently  the  most  diverse  and  weighty  reasons  have 
constrained  authorities  in  most  civilised  lands  to  face  the  problem 
of  excessive  river  pollution,  and  to  require  of  towns  and  factories 
adequate  purification  of  sewage  before  disposal. 

Self -purification  of  Rivers. 

Up  to  a  certain  point,  of  course,  rivers  are  able  to  purify 
themselves  from  the  filth  that  becomes  incorporated.  It  is  by 
no  means  seldom  that  just  beyond  a  town  a  river-course  is  seen 
to  be  very  dirty,  but  that  a  few  miles  further  on  the  water  has 
already  reassumed  a  good  condition.  This  so-called  self -puri- 
fication of  rivers  is  explained  as  being  due  to  a  wonderful  co- 
operation of  physical,  chemical,  and,  above  all,  biological  forces. 
The  suspended  matter  deposited  in  a  river  by  the  sewage  gradu- 
ally settles  to  the  bottom  as  mud.  Here  it  is  disposed  of  by 
snails,  mussels,  insect-larvae,  beetles,  worms,  and  other  organisms, 
which  consume  it,  or  by  continually  loosening  it  prepare  it  for 
a  gradual  washing  away.  Since  the  organisms  mentioned 
represent  the  chief  source  of  nourishment  for  the  fish  feeding  on 
the  river-bed,  it  follows  that  they  can  never  get  the  upper  hand. 
The  dissolved  organic  matter  which  an  effluent  water  carries  to 
a  river,  especially  the  more  molecularly  complex  portions,  and 
therefore  above  all  the  albumens  and  their  decomposition 
products,  are  mainly  decomposed  by  bacteria.  There  then 
appear  Ciliata,  Rotatoria,  and  Infusoria,  which  in  their  turn 
live  on  these  bacteria.  Green  Algae  also  join  in.  These  and  the 
previously  mentioned  groups  are  able  to  absorb  dissolved 
organic  matter  directly  from  the  water.  In  the  main,  however, 
the  green  algae  provide  for  their  own  nourishment  by  assimilating 
carbonic  acid,  nitrates  and  nitrites  which  again  originate  from 
the  activities  of  the  bacteria,  and  from  them  with  the  help  of 
their  green  colouring  matter,  chlorophyll,  they  build  up  the 
necessary  albumens.  During  these  processes  of  assimilation 
oxygen  is  liberated,  and  this  produces  powerful  aeration  of  the 
water.  This  aeration  accounts  for  the  existence  of  the  inhabitants 
of  the  water  already  mentioned,  and  also  for  that  of  the  more 
highly  organised  parts.  The  green  algae,  rotatoria,  ciliata,  and 
infusoria,  etc.,  serve  in  their  turn  as  food  for  the  small  water- 
crabs  or  water-fleas,  and  these  again  play  quite  a  considerable 


66  SEWAGE   DISPOSAL 

part  as  food  for  fish.  So,  finally,  the  sewage  deposited  in  the 
water  is  converted  into  useful  fish. 

Industrial  sewage  containing  heavy  metals  deposits  these  as 
insoluble  sulphides  or  basic  carbonates  on  the  river-bed.  Owing 
to  the  bi-carbonates  present  in  river-water  many  river-waters  have 
a  considerable  capacity  for  neutralising  acid.  The  Maine,  for 
example,  at  Frankfort,  shows  an  average  alkalinity  of  about 
3  cubic  centimetres  of  normal  acid  per  litre  of  water.  Since  with 
the  Maine  at  average  height,  80  cubic  metres  of  water  pass 
through  its  cross  section  per  second,  it  follows  that  the  amount 
of  water  passing  one  point  in  twenty-four  hours  would  be  able 
to  take  up  in  round  numbers  830,000  litres  or  500  tons  of 
concentrated  100  per  cent  sulphuric  acid  without  the  water 
giving  an  acid  reaction.  For  this  it  is,  of  course,  presumed  that 
these  amounts  of  sulphuric  acid  could  mix  thoroughly  with  the 
amount  of  water  under  consideration,  which  naturally  is  not 
possible.  It  always  happens  in  the  introduction  of  acids  into 
river-water  that  only  a  small  portion  of  the  river-water  at  dis- 
posal will  mix  with  the  acid  effluent,  and  the  consequence  is  that 
the  river-water  becomes  acid  over  a  certain  stretch. 

The  same  limitation  operates  as  regards  what  was  said  above 
with  respect  to  the  biological  self-regulating  process.  The 
wonderful  co-operation  of  all  these  forces  and  the  accompanying 
correct  self-purification,  are  only  attained  in  a  satisfactory 
manner  when  the  amount  of  sewage  bears  a  certain  relation  to 
the  purifying  forces.  If  this  relation  is  unsuitable  the  river-bed 
becomes  covered  with  mud  and  with  foul  suspended  matter. 
In  the  water,  large  amounts  of  putrefying  bacteria  appear,  the 
above-mentioned  organisms  do  not  get  their  requirements  of 
life  and  disappear.  When  this  occurs  important  links  in  the 
chain  are  wanting  and  the  orderly  co-operation  of  the  whole  is 
destroyed.  The  water  at  these  stages  will  assume  a  foul  nature 
and  cannot  sufficiently  purify  itself. 

As  a  rule,  good  limiting  values  cannot  be  given  as  regards  the 
amount  of  sewage  that  a  river  can  absorb.  The  amount  of 
effluent  with  which  a  river  may  be  burdened  without  being 
harmed  is  a  question  which  cannot  be  decided  generally,  but  only 
from  case  to  case  with  tests  of  all  the  factors  coming  into  con- 
sideration. In  the  first  place,  for  example,  the  composition  of 
the  sewage  varies  greatly.  Also,  every  river  possesses  its  own 


PURIFICATION    OF   DOMESTIC   SEWAGE  67 

specific  biological  activity,  and  with  that  its  own  specific 
capacity  for  self-purification  which  varies  from  river  to  river. 
Quite  generally  it  may  be  said  that  a  river  can  absorb  more 
sewage  the  more  water  there  is  present,  and  the  greater  the 
velocity  of  that  water.  Demands  as  to  purification  of  sewage 
must  be  correspondingly  stricter  the  smaller  the  flow  of  the  river 
into  which  it  is  to  be  conducted.  On  the  contrary,  large  rivers, 
containing  much  water  affected  by  the  tide,  and  having  a  swift 
current,  can  fully  absorb  sewage  that  is  only  quite  superficially 
purified. 

Sewage  can  be  divided  into  domestic  and  industrial  sewage. 
Domestic  sewage  comprises,  in  the  main,  waters  from  dwelling- 
houses,  containing  therefore  faeces,  cleansing  and  washing  waters, 
kitchen  refuse,  and  similar  substances.  It  is  therefore  rich  in 
easily  decomposable  organic  substances  which  very  soon  become 
foul.  Many  towns,  however,  now  receive  large  amounts  of 
industrial  effluents  into  their  sewage,  and  consequently  in  many 
industrial  towns  the  domestic  sewage  is  often  mixed  with  very 
considerable  quantities  of  industrial  sewage. 

The  sewage  from  many  industrial  concerns  is  characterised, 
as  with  domestic  sewage,  by  a  large  content  of  dissolved  organic 
matter  which  causes  it  to  putrefy  readily.  Many  industrial 
effluents  have,  however,  quite  a  different  composition.  Definite 
information :  on  this  point  cannot  be  given,  since  it  is  dependent 
wholly  on  the  nature  of  the  manufacturing  process. 

Although 'the  particular  methods  of  purification  are  capable 
of  equal  application  in  their  main  features  to  both  classes  of 
sewage,  the  kind  of  purification  necessary  for  normal  domestic 
sewage  is  always  the  same,  while  for  industrial  effluents,  quite 
frequently,  variations  in  the  processes  occur,  adapted  to  the 
individuality  of  the  sewage  coming  at  the  moment  into  question. 
A  distinction  between  the  methods  of  purification  for  domestic 
and  industrial  sewage  is  therefore  to  be  recommended. 

A.  Purification  of  Domestic  Sewage. 

The  different  methods  for  the  purification  of  domestic  sewage 
may  be  thus  distinguished  :— 

Mechanical  purification  (rakes,  screens,  sieves,  grease  extractors, 
grit  chambers,  settling-tanks,  settling-wells,  septic  tanks,  Travis 
and  Emscher  wells). 


68  SEWAGE   DISPOSAL 

Coal-pulp  processes. 

Artificial  biological  purification  (contact  beds  and  percolating 
filters). 

Land  treatment  (broad  irrigation  or  sewage  farming  and 
intermittent  filtration). 

And  lately  also  fish-ponds. 

Mechanical  methods  of  purification  aim  solely  at  the  separation 
of  suspended  matter.  They  have  no  action  on  dissolved  sub- 
stances. 

The  coal-pulp  method,  on  the  contrary,  has  a  small  influence 
on  the  dissolved  matter,  whilst  the  artificial  biological  processes 
and  land  treatment  remove  dissolved  substances  so  largely  that 
the  water  loses  its  capacity  to  putrefy.  There  is  consequently 
this  distinction  between  sewage  purified  mechanically  and  that 
purified  biologically,  that  the  former  becomes  foul  on  standing, 
whilst  the  latter  is  incapable  of  so  doing.  Mechanical  methods 
of  purification  are  therefore  applied  in  those  cases  where,  owing 
to  the  nature  of  the  river  into  which  it  is  run,  the  sewage  need  only 
be  partially  purified.  Dilution  with  large  quantities  of  river- 
water  prevents  a  mechanically  purified  sewage  from  becoming 
foul.  Where  the  ratio  of  river-water  to  sewage  is  small  and  the 
dilution  does  not  guarantee  that  the  purified  sewage  will  not 
putrefy,  biological  treatment  must  be  adopted,  in  which  case  land 
treatment  is  generally  superior  to  artificial  biological  processes. 

I.    MECHANICAL  PURIFICATION   OF  SEWAGE. 

(i)  Rakes,  Screens,  and  Sieves. 

Apparatus  of  this  nature  serves  to  separate  the  undissolved 
substances  over  a  certain  size.  Of  first  importance  are  the 
coarser  floating  substances  such  as  paper,  vegetable  leaves, 
orange-peel,  match-boxes,  corks,  etc.,  which  are  removed  from 
sewage  by  this  treatment.  According  to  Fruhling,  one  under- 
stands by  screens  all  the  particular  varieties  of  such  devices  for 
removing  coarse  suspended  matter,  such  as  bear  the  particular 
names  of  bar-screens,  sieve-screens,  grating-screens,  etc.  Bar- 
screens  consist  of  bars  set  parallel  to  one  another,  grating-screens 
of  wires  crossing  each  other,  and  sieve-screens  of  a  network  of 
wires  or  of  perforated  metal  plates. 


RAKES,    SCREENS,    AND    SIEVES 


69 


There  are  both  coarse  and  fine  screens.  Coarse  screens  are 
mostly  iron  rods  about  10  to  20  centimetres  apart,  obliquely 
placed  at  an  obtuse  angle  to  the  surface  of  the  water.  These 
only  serve  to  keep  back  the  coarsest  suspensions,  such  as  tin 
boxes,  the  larger  pieces  of  wood,  large  pieces  of  entrails,  large 
rags,  and  the  like. 

Fine  screens  are  generally  stationary,  or  automatically  moving 
apparatus.  Stationary  screens  are  mostly  bar-screens,  also 


FIG.  13.     UHLFELDER'S  REVOLVING  SCREEN. 

consisting  of  bars  laid  alongside  one  another,  and  placed  at  an 
obtuse  angle  to  the  surface  of  the  water.  The  distance  of  the 
bars  apart  is,  however,  considerably  less  than  with  coarse  screens, 
usually  between  10  and  25  millimetres.  The  water  flows  against 
these  bars  and  leaves  there  substances  of  larger  size.  Movable 
screens  differ  from  the  stationary  type  in  that  they  are  driven 
through  the  water  and  fish  out  the  floating  material.  Of  the  best 
constructed  and  most  frequently  used  movable  bar-screens  in 
municipal  clarifying  plants  (Frankfort,  Elberfeld)  is  the  Uhlfelder 
Revolving  Screen  (Fig.  13).  It  is  a  circular  revolving  screen, 


70 


SEWAGE   DISPOSAL 


composed  of  five  single  screens,  which  rotate  uniformly  against 
the  current  of  water.  The  coarser  matter  floating  upon  or 
suspended  in  the  water  is  removed  by  the  screens  while  in  motion 
and  is  raised  out  of  the  water.  An  automatic  brush  follows 
which,  pressing  through  the  screen,  brushes  it  outwards  and  casts 
the  material  on  to  a  platform  underneath.  This  is  then  tipped 
up  by  the  motion  of  the  screens  and  empties  the  contents  on  to 
a  travelling  platform  which  carries  the  material  away.  With  such 


FIG.  14.     RIEN  SIEVE. 

screens  the  work  is  purely  automatic  and  the  purification  me- 
chanical.   Other  kinds  of  screens  may  be  cleaned  by  hand,  fr 

Among  automatically  working  sieve-screens  the  Rien  has 
frequently  been  employed.  It  is  used  to  screen  Dresden  sewage, 
which  is  then  run  into  the  Elbe  without  further  treatment. 
The  Rien  apparatus,  as  is  shown  in  Figure  14,  consists  of  a 
metal  disc  set  obliquely  in  the  water  and  composed  of  sheet- 
metal  sieving  or  sieve  plates.  In  the  centre  of  the  disc  there  is 
placed  a  truncated  cone  of  the  same  material.  The  water  flows 
against  the  disc,  which  is  continually  turning.  As  a  consequence 
the  suspended  filth  remains  on  the  disc,  whilst  the  water  passes 


RAKES,   SCREENS,   AND   SIEVES 


71 


through  the  openings.  Owing  to  the  motion  of  the  disc,  the 
sludge  is  removed  from  the  water,  and  then  scraped  away  from 
the  screens,  and  from  the  truncated  cone  also,  by  means  of 
brushes. 


FIG.  15.     KREMER  APPARATUS. 


a,  Inlet  channel,  b,  Lateral  inflow  pipes,  c,  Space  for 
attaining"  an  upward  thrust  in  the  water.  d,  Grease  ex- 
tractor, e,  Floating-  layer  rich  in  fat.  ft  Clarifying-  space. 
g-,  Reversal  of  the  direction  of  the  water  at  the  edg-e  of  the 
circular  partition,  h,  Circular  overflow  channel,  an  outlet 
for  the  clarified  water.  i,  Sludge  cylinder.  kt  Sludg-e 
drain.  /,  Cleansing-  pipe. 


72  SEWAGE    DISPOSAL 

(iiV  Grease  Extractors. 

Many  effluents,  such  as  those  from  slaughter-houses,  kitchens, 
and  other  similar  places,  contain  a  large  amount  of  grease. 
Since  the  fats  are  lighter  than  water  they  cannot  be  separated 
in  grit-chambers,  settling-basins,  and  other  contrivances.  They 
can,  however,  be  removed  from  sewage  in  grease  extractors,  and 
in  certain  circumstances  these  allow  of  a  recovery  of  the  grease. 

There  is  a  whole  series  of  plants  for  the  recovery  of  grease. 
The  best  known  of  these  is  the  Kremer  apparatus.  This  apparatus 


FIG.  16.     GREASE  EXTRACTORS  OF  THE  "  STADTEREINIGUNG 
FIRM"  OF  BERLIN-WIESBADEN. 


can  also  be  used  independently  as  a  clarifying  plant,  since  it  also 
separates  from  the  sewage  any  suspended  matter  that  is  heavier 
than  water.  The  apparatus  (Fig.  15)  separates  the  undissolved 
substances  by  means  of  a  peculiar  motion  of  the  stream  working 
in  such  a  way  that  the  substances  are  divided  into  two  layers  of 
sludge,  according  to  their  specific  gravity.  Grease  particles 
adhering  to  light  organic  matter  form  the  upper  floating  layer, 
whilst  the  lower  layer  is  composed  of  the  heavy  particles  of 
suspended  matter.  According  to  Vogelsang,  the  Kremer  ap- 


GRIT   CHAMBERS  73 

paratus  is  to.  be  recommended  strongly  for  preliminary  purifi- 
cation with  the  biological  processes,  since  it  separates  much  of 
the  light  suspended  matter,  such  as  grease,  paper,  straw,  and  the 
like,  which  cannot  be  removed  by  sedimentation  processes,  and 
which  consequently  choke  up  the  contact  beds  and  percolating 
filters  with  mud.  The  "Gesellschaft  fur  Abwasserklarung  "  (Sew- 
age Clarifying  Co.),  of  Berlin-Schoneberg,  supply  this  apparatus. 
The  firm  also  employ  them  in  combination  with  Emscher  wells 
(see  page  82  in  this  book) .  They  call  the  combination  the  Kremer- 
Faulbrunnen  (Kremer  septic  well),  and  warmly  commend  its 
great  utility. 

A  grease  extractor  of  another  type  is  that  of  the  "  Stadter- 
einigung  und  Ingenierbau  A.-G."  firm  of  Berlin- Wiesbaden. 
As  shown  in  Figure  16,  the  greasy  water  enters  through  the 
funnel  c  into  the  space  d,  where  by  means  of  a  deflector  e  it  is 
uniformly  divided  and  diverted  in  direction  upwards.  The 
particles  of  grease  have  time  to  separate  out  in  the  upper 
parts  of  d,  whilst  a  quantity  of  water  in  the  space  d,  corresponding 
to  the  inflow  from  above,  passes  out  below  through  the  circular 
opening  F.  The  sludge  sinks  lower  and  falls  eventually  into  the 
sludge-pail  g,  whilst  the  water,  freed  from  grease  and  mud,  rises 
to  the  brim  of  the  reservoir  and,  overflowing  at  i,  passes  into  the 
outlet  pipe  at  z. 

Of  other  systems  the  grease  extractors  of  Kaibel,  Darmstadt, 
of  Kremer-Schilling,  and  of  Heyd,  Darmstadt,  may  also  be  named. 

(iii)  Grit  Chambers. 

Many  plants  for  preliminary  purification  also  make  use  of 
grit  chambers.  Whilst  screening  removes  the  coarser  floating 
matter,  grit  chambers  are  intended  to  separate  the  heavier  and 
coarser  sinking  suspensions.  This  is  attained  by  allowing  the 
pipe  conveying  the  water  to  the  clarifying  plant  to  suddenly 
discharge  its  contents  into  a  larger  space  known  as  the  grit 
chamber.  As  a  result,  the  velocity  of  the  sewage,  owing  to  the 
increase  in  cross  section  of  the  chamber,  is  quite  considerably 
reduced.  Consequently  the  coarse  suspensions,  like  rags,  bones, 
sand,  and  such-like,  settle  to  the  bottom.  The  cross  section  of  grit 
chambers  varies  greatly.  They  may  be  funnel-shaped  or  rect- 
angular, or  they  may  have  arched  bottoms,  etc.  The  mud  which 


74  SEWAGE   DISPOSAL 

settles  is  removed  either  by  hand  or  mechanically,  and  the 
removal  may  take  place  either  after  emptying  or  during  the 
process.  The  mechanical  sludge-remover  generally  consists  of 
a  dredging-machine,  which  dredges  the  sludge  and  casts  it  on  to 
a  travelling  platform.  With  grit  chambers  built  funnel-shaped, 
the  dredger  can  remain  standing  in  the  one  place.  With  other 
forms  the  dredger  can  often  be  moved  from  one  end  of  the 
chamber  to  the  other,  as  at  Frankfort-on-Maine.  According 
to  the  investigations  of  the  author  in  Frankfort,  with  a  good  grit 
chamber  and  a  system  of  fine  screens,  about  one-fifth  of  the 
total  suspension  in  a  sewage  is  removed. 

(iv)  Sedimentation  Tanks,  Wells,  and  Towers. 

These  contrivances  serve  for  the  deposition  of  the  finer  sus- 
pended matter.  The  sewage  is  simultaneously  introduced  into 
a  number  of  such  tanks  or  wells,  so  that,  owing  to  the  increased 
cross  section,  the  velocity  of  water  is  very  considerably  di- 
minished, and  consequently  the  finer  particles  of  suspended 
matter  can  settle  to  the  bottom. 

Sedimentation  tanks  are  generally  elongated  rectangular 
chambers,  constructed  either  open  or  covered,  though  they  are 
most  frequently  open.  They  are  generally  about  40  metres  long, 
but  there  are,  however,  sedimentation  tanks  considerably  shorter 
and  longer.  The  inflow  generally  occurs  through  openings 
situated  below  the  surface  of  the  water,  in  order  that  the  already 
precipitated  sludge  shall  not  be  disturbed  by  the  motion  of  the 
water.  The  beds  of  the  tanks  are  built  both  rising  and  falling 
towards  the  outlet.  According  to  the  researches  of  Steuernagel 
and  Grosze-Bohle,  the  rising  bed  has  proved  satisfactory  for 
sedimentation  work.  Generally  at  either  inlet  or  outlet,  or  even 
at  both  places,  sump-pumps  are  placed  to  pump  away  the 
deposit  which  collects  there.  The  Frankfort  sedimentation  tanks 
are  40-6  metres  long  and  have  pumps  at  7-5  metres  distance  from 
the  inlet  and  outlet.  The  chamber  bottom  is  so  constructed 
that  in  the  middle  it  is  raised  and  falls  away  with  a  fall  of  i  in  10 
to  the  sumps.  There  is  the  same  fall  from  both  inlet  and  outlet. 
This  arrangement  of  the  chamber  bottom  serves  to  lead  the  mud 
of  itself  to  the  pumps,  through  which  it  is  removed.  This  renders 
superfluous  the  cleaning  of  the  tank  bottoms  with  shovels  or 


SEDIMENTATION   TANKS,   ETC. 


75 


similar  contrivances.     In  Figure  17  the  form  of  the  Frankfort 
sedimentation  tank  is  shown  in  cross  section. 

It  was  formerly  thought  that  to  effect  good  sedimentation  the 
chambers  must  be  built  so  large  that  the  velocity  of  the  water 


FIG.  17.     FRANKFORT  SEDIMENTATION  TANK  (CROSS  SECTION). 

would  be  extraordinarily  small  (2  to  4  mm.  per  second).  Ex- 
periments of  Grosze-Bohle  in  Cologne  have  shown,  however,  that 
with  a  velocity  of  20  to  40  millimetres  the  same  sedimentation 
is  attained.  Also  in  Frankfort  it  could  be  demonstrated  that 


76  SEWAGE   DISPOSAL 

the  abnormally  small  velocity  of  2  to  4  millimetres  per  second 
gave  no  better  results  than  one  of  12  millimetres  per  second. 
With  higher  velocities  than  12  millimetres  per  second  considerable 
diminution  of  the  sedimentation  was  obtained,  so  that  one 
cannot  generalise  on  the  results  from  Cologne  without  further 
details.  According  to  Schiele,  in  England  they  still  keep  quite 
generally  to  the  small  velocity  of  2  to  4  millimetres. 

In  the  settling  tanks  there  also  separate  out  a  number  of  floating 
substances  which  are  composed  firstly  of  the  fatty  matter  in  the 
sewage,  and  secondly,  especially  when  the  tanks  have  been  in 
use  for  a  long  period,  of  particles  of  sludge  rising  up  on  account 
of  fermentation.  In  order  to  avoid  admitting  these  floating 
particles  into  the  outlet,  a  board  is  generally  partially  immersed 
in  the  water  and  set  obliquely  a  short  distance  in  front  of  the 
outlet.  The  particles  collect  in  front  of  this. 

The  mud  is  generally  disposed  of  first  by  running  off  all  the 
water.  The  sludge  is  then  pumped  away  from  the  slime  deposit. 
In  some  sedimentation  plants  sludge-pumps  working  under 
water  might  be  tried  ;  these  naturally  would  be  advantageous 
in  that  the  sludge  could  then  be  removed  during  the  sedimenta- 
tion process  without  the  chamber  that  is  to  be  purified  being 
emptied.  In  general,  however,  sludge-pumps  do  not  appear  to 
have  worked  well.  The  main  difficulty  lies  in  this,  that  the 
sludge  does  not  slip  along  sufficiently  towards  the  pumps  ;  on 
the  contrary,  a  crater  is  often  formed  in  the  sludge  and  the 
sewage  is  suddenly  sucked  over  instead  of  the  sludge. 

The  settling  process  is  frequently  assisted  by  the  addition  of 
chemicals.  Alum  and  lime,  or  ferrous  sulphate  and  lime,  and 
other  substances  are  used.  The  principle  upon  which  the  use 
of  these  substances  is  based  is  as  follows :  The  chemicals  form 
gelatinous  and  voluminous  precipitates  (alum  -f lime = gypsum 
and  aluminium  hydroxide),  which  on  sinking  to  the  bottom  carry 
the  suspended  matter  along  with  them.  The  chemicals  have 
also  a  slight  action  on  the  dissolved  organic  matter.  This  action, 
according  to  some,  will  be  insignificant  in  itself,  the  main  action 
being  the  assistance  which  the  chemicals  render  towards  settling 
out  the  suspensions.  With  domestic  sewage  the  action  of 
chemicals  is  frequently  denied.  Thus,  parallel  experiments  have 
been  carried  out  by  Lepsius  and  later  by  Freund  in  Frankfort- 
on-Maine  with  chemical  precipitation  and  with  purely  mechanical 


SEDIMENTATION   TANKS,   ETC.  77 

sedimentation,  by  which  it  was  established  that  the  influence  of 
chemicals  on  sedimentation  was  practically  insignificant.  Accord- 
ing to  Schiele,  however,  in  opposition  to  this  view,  the  addition 
of  chemicals  to  domestic  sewage  is  still  practised  in  England. 
In  the  author's  opinion  chemicals  certainly  have  an  effect  on 
the  dissolved  substances,  and  also  act  in  the  case  of  domestic 
sewage  on  the  pseudo-dissolved  substances,  the  colloids,  to  no 
inconsiderable  extent.  Aluminium  hydroxide  and  ferric  hy- 
droxide are,  as  is  well  known,  also  colloids,  and  have  an  adsorbent 
action  on  the  colloids  in  the  sewage.  Frequently,  addition  of 
chemicals  to  industrial  effluents  must  be  made.  The  main 
drawbacks  to  the  addition  of  chemicals  are  the  considerable 
increase  in  cost  of  the  sedimentation  process,  and  the  difficulty 
of  disposing  of  the  sludge.  The  sludge  obtained  when  chemicals 
are  used  is,  in  the  first  place,  far  more  aqueous,  and  so  takes  up 
much  more  room,  while  secondly,  on  account  of  the  sludge 
containing  chemical  substances,  which  at  least  are  indifferent  from 
the  manurial  point  of  view,  it  is  considerably  depreciated  in  value 
as  a  manure.  The  amount  of  chemicals  added  varies  greatly 
according  to  the  composition  of  the  sewage  to  be  purified.  It 
varies  between  about  43  and  950  grammes  per  cubic  metre  (7  to 
150  oz.  per  1000  gallons)  of  sewage.  The  chemicals  are  added 
either  in  the  liquid  or  solid  state.  In  the  liquid  form  it  is  allowed 
to  flow  into  the  sewage  in  a  thin  stream.  When  applied  in  solid 
form  the  chemicals  are  added  to  the  water  in  wire  baskets,  so 
that  the  water  flowing  through  dissolves  out  the  chemicals.  For 
these  to  work  properly  it  is  of  great  importance  that  care  be  taken 
to  get  good  mixing  between  chemicals  and  sewage.  If  there  be 
sufficient  space  between  the  place  of  addition  and  the  settling 
tanks,  the  water  itself  ensures  adequate  mixing.  Now  and  again, 
however,  various  devices  are  employed  to  attain  good  mixture. 
Thus,  tongues  are  placed  in  the  sewage-pipe,  by  which  means  the 
water  is  broken  up. 

The  amount  of  suspended  matter  separated  out,  expressed  as 
a  percentage  of  the  total  content  of  suspended  matter  in  the 
crude  sewage,  amounts,  with  good  sedimentation  tanks  and  not 
too  high  a  velocity  (12  mm.)  in  the  basins,  to  60  or  70  per  cent. 

Sedimentation  wells  and  towers  are  generally  cylindrical  in 
form  and  are  distinguished  essentially  from  tanks  in  that  the 
water  flows  through  them  upwards  and  in  a  vertical  direction, 


78  SEWAGE   DISPOSAL 

whereby  the  suspended  matter  settles  out  underneath.  In  such 
sedimentation  reservoirs  the  velocity  of  the  sewage  is  generally 
considerably  less  than  in  sedimentation  tanks.  With  towers  and 
wells  the  sludge  can  be  removed  more  easily  while  the  process  is 
in  operation  than  is  possible  with  tanks,  since  it  is  in  such  cases 
more  conveniently  concentrated  into  a  certain  space.  To  guard 
against  the  water  breaking  through  (see  page  76),  various  con- 
structions have  been  proposed,  based  on  the  closing  of  the  water 
space  whilst  the  sludge  is  being  pumped  off. 

(v)  Septic  Tanks. 

Septic  tanks  are  only  employed  as  preliminary  purifiers  in 
biological  purification  plants  ;  they  do  not  come  into  considera- 
tion as  separate  clarifying  plants.  They  are  employed  in  a 
manner  similar  to  the  usual  sedimentation  tanks,  but  with  the 
difference  that  the  sludge  which  separates  out  is  allowed  to  lie 
for  a  long  period.  It  is  thereby  converted  into  a  foul  state  of 
fermentation,  which  is  then  communicated  to  the  sewage.  The 
sewage  is  coloured  black,  owing  to  the  presence  of  ferric  sulphide, 
and  assumes  a  very  foul  odour.  As  a  result  of  the  activity  of 
the  fungi  setting  up  putrefaction  a  portion  of  the  organic  matter 
is  decomposed.  There  forms  on  the  septic  tank  after  a  short 
time  a  scum  consisting  of  grease  mixed  with  particles  of  sludge 
raised  by  the  fermentation.  This  scum  shuts  off  the  air  from  the 
sewage,  and  is  of  great  importance  in  the  putrefactive  action 
which  is  caused  by  anaerobic  bacteria.  In  some  English  septic- 
tank  installations  the  floating  layer,  according  to  Schiele,  now 
and  then  becomes  so  strong  that  one  can  actually  walk  upon  it. 

Moreover,  these  septic  tanks  act  like  sedimentation  tanks  as 
regards  removal  of  suspended  matter.  With  the  slow  passage  of 
the  water  through  the  septic  tanks  the  suspensions  settle  out. 
A  certain  amount  of  time  always  elapses  before  a  septic  tank  is 
in  good  working  order,  that  is,  until  it  yields  a  thoroughly 
putrefied  effluent.  Septic  tanks  are  built  both  open  and  covered. 
The  open  tanks  have  the  drawback  that  they  cause  annoyance 
from  their  smell.  Septic  tanks,  according  to  Schiele,  must  be 
capable  of  holding  at  least  half  a  day's  dry- weather  drainage. 
Smaller  plants  are  generally  built  large  enough  to  hold  from 
three  to  six  times  the  dry- weather  discharge. 


TRAVIS   AND   EMSCHER   WELLS  79 

Naturally  the  removal  of  sludge  takes  place  less  frequently  in 
this  case  than  with  the  usual  settling  tanks.  It  is  useful  never 
to  remove  the  whole  of  the  sludge,  but  always  to  leave  some  still 
lying ;  the  tank  then  gets  into  working  order  afresh  more  quickly, 
because  the  putrefactive  fungi  from  the  thoroughly  putrefied 
sludge  can  more  easily  communicate  themselves  to  the  sewage. 

The  main  advantages  of  septic  tanks  may  be  thus  noted.  In 
the  first  place,  the  sludge  need  not  be  removed  so  often,  which 
naturally  means  cheaper  working ;  and  secondly,  the  sludge  from 
septic  tanks,  especially  according  to  the  results  of  recent  work, 
is  by  no  means  so  disagreeable  as  the  sludge  from  the  usual 
sedimentation  tanks.  It  is  more  easily  freed  from  water  and 
contains  a  considerably  larger  bulk  of  dry  substances.  These 
relations  will  be  more  carefully  dealt  with  in  the  chapter  on 
sludge.  As  a  further  advantage  of  septic  tanks,  there  has  to  be 
considered  the  decomposition  of  a  portion  of  the  organic  sub- 
stances which,  from  the  observations  of  Dunbar  and  his  pupils, 
takes  place  both  in  the  sewage  and  the  sludge. 

With  septic  tanks  there  is  the  disadvantage  that  the  effluent 
is  not  so  completely  freed  from  suspended  matter  as  with  sedi- 
mentation tanks.  Owing  to  the  fermentation  set  up  in  the  sludge, 
fine  particles  are  propagated  upwards  and  so  pass  into  the  dis- 
charge. Since  suspended  matter  vitiates  bacterial  action  in 
contact  beds  and  percolating  filters  to  a  considerable  degree,  and 
also  causes  their  more  rapid  pollution,  sieves  are  often  placed  in 
the  discharge-pipe  to  check  this  annoying  feature. 

(vi)  Travis  and  Emscher  Wells. 

These  apparatus  are  distinguished  from  sedimentation  and 
septic  tanks  by  the  separation  of  the  sludge  from  the  actual 
sedimentation  space. 

According  to  Collins  ("  Surveyor,"  1909),  the  Travis  plant  in 
Norwich  consists  of  rectangular  tanks,  whose  lower  parts  are 
wedge-shaped  in  cross  section  (see  Fig.  19).  Lengthways  in  each 
tank  a  roof  is  built,  which  is  cut  open  at  the  coping  in  the  long 
axis  of  the  tank  and  is  carried  upwards  above  such  axis.  Where 
the  roof  is  joined  to  the  tank- walls  and  to  the  coping,  gaps  are 
left.  Through  these  gaps  the  three  compartments  of  the  tank, 
arising  out  of  the  mode  of  construction,  are  in  communication 


80 


SEWAGE   DISPOSAL 


with  one  another.  Both  the  outer  compartments  serve  as  sedi- 
mentation compartments.  The  sludge  on  settling  out  slides 
down  the  sloping  surface  formed  by  the  roof  and  falls  through 
the  gaps  into  the  middle  section  of  the  tank,  the  reduction  or 
sludge  chamber.  In  the  central  portion  of  the  settling  tank  there 
are  placed  grating-like  frames  (colloiders)  about  10  inches  from 
each  other.  These  devices  should  serve  to  retain  and  to  exert  a 
certain  coagulating  influence  on  the  colloids ;  80  per  cent  of  the 
sewage  enters  through  the  two  outer  settling  tanks,  whilst  20  per 
cent  enters  the  reduction  chamber  or  sludge  area  through  the 
openings  at  the  coping  of  the  roof.  The  water  passes  out  over 


FIG.  1 8.     CLEARING  WELL  INSTALLATION  AT  NORWICH  ON  THE  TRAVIS 
HYDROLYTIC  SYSTEM,  WITH  COLLOIDER  HUNG  IN. 

(From  "  Wasser  und  Abwasser,"  1909-10,  II,  71.) 

a  weir  which  occupies  the  whole  breadth  of  the  tank,  and  which, 
corresponding  to  the  three  tanks,  is  three-sided.  The  effluent 
from  the  liquefying  chamber  is  subsequently  purified  in  a  special 
tank  provided  with  "  colloiders  "  like  the  sedimentation  tank. 
The  removal  of  sludge,  necessary  from  time  to  time,  is  con- 
veniently attained  by  having  the  bed  of  the  sludge  chamber 
composed  of  a  number  of  funnels.  The  walls  of  these  funnels  are 
so  inclined  that,  on  opening  the  outlet  situated  at  the  lowest 
point  of  the  shoulder,  the  sludge  is  pressed  out  by  means  of  the 
pressure  of  water  above. 

Travis  tanks  have  come  into  use  considerably,  especially  in 
England,  and  presumably  have  proved  excellent.  The  main 
difference  between  the  Travis  tank  and  Emscher  wells  consists 


PI  an 


FIG.  19.     EMSCHER  WELLS. 

Arrangement  of  several  wells  with  settling-  channel  in  common.  Re- 
moval of  sludge  by  excess  water  pressure  to  the  lower  lying  sludge 
storage  grounds. 

A,  Inlet.  B,  Screening  chamber,  e,  Channel  for  screenings  it,  Cir- 
culating channel.  P,  Outlet.  Z>,  Fume  Chamber.  G,  Partitions. 
?/,  Waste-weir.  Fl  and  F2,  Liquefying  chambers.  J?,  Sludge  pipe. 
S,  Cleansing  pipe. 

G 


82  SEWAGE   DISPOSAL 

in  this,  that  with  the  former  from  time  to  time  fresh  water  is 
purposely  led  through  the  liquefying  chamber  in  order  to  remove 
the  liquid  constituents  of  the  sludge  generated  by  the  putre- 
faction. With  Emscher  wells  the  principle  is  to  avoid  any 
flushing  of  the  liquefying  chamber. 

Emscher  wells  (Fig.  19)  consist  in  the  main,  according  to 
Middledorf ,  of  deep  wells  which  are  intended  for  the  reception  of 
the  sludge.  In  the  upper  part  of  these  wells  by  means  of  a  partition- 
wall  a  settling  tank  or  well  is  apportioned  off,  and  through  this  the 
water  flows.  As  soon  as  it  touches  the  sloping  bottom  the  sludge, 
settling  out  in  the  tank,  flows  of  itself  through  gaps  at  the  lowest 
parts  of  the  sedimentation  space  into  the  sludge  wells.  The 
water  flows  only  through  the  sedimentation  area  and,  in  agree- 
ment with  the  principle,  not  through  the  putrefactive  area.  The 
putrefaction  is  thereby  confined  to  the  sludge  alone,  and  the 
water  flowing  away  is  obtained  as  fresh  as  possible,  unmixed  with 
any  of  the  polluted  water.  The  amount  of  water  from  the 
sludge  which  gains  access  to  the  sewage  should  amount  to  about 
one  part  in  a  thousand.  With  variation  of  temperature  also  there 
should  be  little  tendency  for  water  from  the  sludge  to  rise  into 
the  sedimentation  tank,  since  it  is  specifically  heavier  than  fresh 
sewage.  As  the  sludge  from  the  settling  tanks  is  withdrawn 
uninterruptedly  and  automatically,  there  is  absolute  certainty 
that  it  is  always  removed  at  the  right  time  and  does  not  remain 
lying  in  the  settling  tanks,  injuring  the  clarifying  process  by  its 
foulness.  The  particles  of  mud  propagated  upwards  by  fer- 
mentation cannot  pass  through  the  clefts  in  the  partition-wall, 
but  are  forced  against  the  wall  underneath  the  sewage  and  sink 
again  from  there  to  the  bottom.  The  sedimentation  in  Emscher 
wells  should  be  equally  as  good  as  with  other  good  settling  plants 
with  the  same  period  of  sedimentation.  The  sludge  putrefies  in 
the  liquefying  chamber,  and  thereby  becomes  more  suitable  for 
disposal  (see  under  Sludge).  The  fact  that  water  is  not  allowed 
to  flow  through  the  chamber  has  not  proved  a  hindrance  to  the 
putrefaction  of  the  sludge.  It  is  because  of  this  that  the  freshness 
of  the  water  to  be  purified  is  maintained,  and  it  may  be  reckoned 
an  advantage  in  the  process.  With  Emscher  wells,  in  contra- 
distinction to  other  liquefying  chambers  through  which  the  water 
is  allowed  to  flow,  scarcely  any  trace  of  sulphuretted  hydrogen  is 
evolved.  According  to  the  investigations  of  Spillner,  the  gases 


TRAVIS   AND   EMSCHER   WELLS  83 

which  escape  from  the  liquefying  chamber  and  pass  both  through 
the  sewage  and  around  the  sedimentation  tanks  consist  mainly 
of  methane  and  carbon  dioxide.  Odourlessness  of  the  sludge 
should  be  attained  equally  well  with  purely  domestic  sewage 
purifiers,  and  with  plants  receiving  industrial  effluents.  The 
sludge  is  led  through  pipes  from  the  liquefying  chamber  to  the 
sludge  drying-place.  The  end  of  the  pipe  reaches  to  the  lowest 
point  of  the  funnel-shaped  bed  of  the  well.  Only  the  under- 
neath portion  of  the  most  thoroughly  putrefied  sludge  is  led  away. 
If  the  area  for  drying  the  sludge  can  be  situated  from  1-5  to  2 
metres  lower  than  the  water-level  in  the  wells  the  sludge  can 
then  be  removed  by  the  natural  fall,  since  for  this  purpose  a  head 
of  i  metre  is  generally  sufficient.  If  this  head  cannot  be  obtained 
the  sludge  is  removed  either  by  a  Wagner  suction  apparatus, 
with  a  hand  or  air-pressure  pump,  or  with  a  vacuum  plant 
driven  by  an  air-pressure  pump.  In  all  plants  of  the  Emscher 
Co.  the  sludge  should  be  displaced  through  the  sludge-pipes 
without  any  difficulty.  The  reason  for  this  is  largely  because  the 
sludge  during  the  septic  action  loses  its  felt-like  nature  and 
forms  a  black,  pulpy,  fluid  mass,  in  spite  of  its  low  per- 
centage of  about  70  to  80  per  cent  water.  The  removal  of  the 
sludge  takes  place  perhaps  once  every  two  or  three  months.  The 
liquefying  chamber  should  be  so  large  that  it  can  hold  the  sludge 
falling  in  during  this  length  of  time. 

Meanwhile,  the  question  of  Emscher  wells  has  been  vigorously 
debated  in  the  literature.  In  the  main  the  following  points  have 
been  contested  :  Whether  the  plant  is  practically  odourless  ; 
whether  the  sedimentation  is  as  good  in  Emscher  wells  as  in 
other  good  sedimentation  plants  ;  whether  liquefaction  actually 
occurs  in  the  sludge  ;  whether  the  water  remains  at  rest  in  the 
liquefying  chamber,  or  whether  rather,  just  so  much  of  the 
polluted  water  from  the  liquefying  chamber  enters  the  sedi- 
mentation tank  as  sludge  separates  out. 

It  must  be  pointed  out,  however,  that  Emscher  wells  are  com- 
ing more  than  ever  into  application,  both  as  separate  sedimenta- 
tion plants  and  also  as  plants  for  the  preliminary  purification  of 
sewage  about  to  be  bacterially  treated. 

The  main  advantage  of  Travis  and  Emscher  wells  over  the 
usual  sedimentation  tanks  is  therefore  the  simplicity  with  which 
the  sludge  problem  is  solved. 


84  SEWAGE    DISPOSAL 

'  There  is  this  great  advantage  in  a  joint  plant  working  with 
automatic  separation  of  sludge.  A  small  velocity  of  sedimenta- 
tion can  be  chosen  without  the  process  becoming  more  difficult 
as  regards  the  handling  and  disposal  of  large  amounts  of  thin 
sludge  containing  high  percentages  of  water,  such  as  generally 
settle  out  under  such  conditions  "  (Schmidtmann,  Thumm,  and 
Reichle). 

II.     DEGENER'S   COAL-PULP   PROCESS. 

As  regards  the  nature  of  its  action,  this  method  stands  midway 
between  the  mechanical  and  the  bacterial  methods,  for  like  the 
former  its  main  action  depends  on  the  removal  of  the  suspended 
matter,  and  like  the  latter  it  has  an  undoubted  action  on  the 
dissolved  substances. 

I  to  2  kilograms  of  ground-peat  or  2-5  to  4  kilograms  of  turf 
are  added  to  a  cubic  metre  of  the  sewage  to  be  purified.  Chemicals, 
such  as  aluminium  or  ferric  sulphates,  are  simultaneously  added. 
Generally,  the  sewage  is  then  allowed  to  settle  in  sedimentation 
towers.  The  sludge  is  fairly  aqueous,  but  is  usually  freed  from 
water  in  filter-presses,  and  in  this  case  is  then  no  longer  capable 
of  putrefaction.  The  air-dried  sludge,  on  account  of  its  high 
carbon  content,  is  a  valuable  burning  material.  Lately  it  has  been 
rendered  more  valuable  by  gasification  (see  under  Sludge) . 

The  whole  process  should  work  without  smell,  and  on  this 
account,  and  because  the  troublesome  sludge  question  with  its 
dangers  is  obviated,  it  is  a  method  of  great  importance.  The 
further  advantage  of  a  reduction  in  the  dissolved  organic  sub- 
stances has  been  referred  to  previously.  Against  these  advan- 
tages there  is  the  main  disadvantage  of  cost,  which  is  very 
considerable.  It  is  because  of  this  that  the  number  of  plants 
working  the  process  on  a  large  scale  remains  so4imited,  in  spite 
of  the  method  being  so  superior. 

III.     BACTERIAL   PURIFICATION   OF   SEWAGE. 

As  already  mentioned,  the  dissolved  organic  matter  is  un- 
changed in  a  mechanically  purified  sewage.  If  such  an  effluent 
be  allowed  to  stand  for  some  time  it  very  soon  begins  to  putrefy 
and,  from  the  plentiful  development  of  putrefactive  bacteria, 
assumes  a  stinking  condition. 


ARTIFICIAL   BIOLOGICAL   METHOD  85 

The  task  of  bacterial  sewage  purification  is  so  far  to  remove 
the  dissolved  organic  matter  from  the  sewage  that  putrefaction, 
with  its  accompanying  disagreeable  phenomena,  is  avoided.  As 
the  name  indicates,  in  bacterial  purification  processes  bacterial 
agencies  come  into  play. 

In  particular  two  processes  are  distinguishable,  viz.  artificial 
biological  sewage  treatment,  and  broad  irrigation  or  sewage 
farming. 

(i)   The  Artificial  Biological  Method. 

Artificial  biological  sewage  purification  is  the  designation 
applied  to  that  treatment  whereby,  after  suitable  preliminary 
purification  by  mechanical  methods  as  detailed  in  Part  I,  the 
sewage  is  led  over  large  pieces  of  slag,  coke,  or  similar  materials. 
The  organic  matter  is  by  this  means  so  far  removed  from  the 
sewage  as  to  prevent  subsequent  putrefaction  in  the  effluent. 

Biological  processes  for  the  treatment  of  sewage  arose  in 
England,  where  they  were  first  used  and  tested  on  a  large  scale. 
That  this  method  was  first  improved  in  England  is  quite  reason- 
able, since  England  is  the  classic  country  for  sewage  disposal. 
In  consequence  of  the  peculiar  circumstances  operating  there, 
its  position  as  the  premier  country  in  the  world,  England  was 
compelled  to  work  out  good  methods  of  sewage  purification. 
The  largest  English  rivers  have  not  the  capacity  and  velocity 
even  of  our  Spree  or  Havel  (tributaries  of  the  Elbe,  Trans.}.  With 
industry  flourishing  in  the  middle  of  the  last  century  there  went 
hand  in  hand  alarming  pollution  of  the  whole  river  system  of 
England. 

Thorough  preliminary  purification  is  of  vital  importance  for 
the  continued  good  working  of  biological  processes.  Grit  cham- 
bers, screening,  'and  the  mechanical  purification  involved  in 
sedimentation  and  septic  tanks,  all  come  into  consideration. 
For  domestic  effluents  the  sewage  is  generally  first  purified  in 
sedimentation  or  septic  tanks.  If  much  industrial  effluent  be 
admixed  with  the  household  sewage,  chemical  treatment  is 
generally  indispensable.  Moreover,  it  is  advisable  to  find  out  in 
each  case,  by  special  experiments,  the  most  suitable  preliminary 
treatment  for  the  sewage. 

Many  substances  are  used  as  material  for  the  beds  employed 
in  these  biological  processes.  Clinkers  from  refuse  destructors, 


86  SEWAGE   DISPOSAL 

slag,  earthenware,  bricks,  coke,  pieces  of  slate,  and  such-like 
materials  have  all  been  tried.  According  to  Schiele,  the  main 
requirements  in  such  a  material  are  great  hardness,  capacity  to 
withstand  the  action  of  sewage,  roughness,  and  firmness. 

Large  beds  are  laid  down  composed  of  lumps  of  these  materials 
loosely  collected  together.  Distinction  must  be  made  between 
contact  beds  and  percolating  niters.  The  distinction  between 
the  two  lies  in  the  manner  of  their  impregnation  with  sewage. 
Contact  beds  are  filled  with  sewage  ;  the  sewage  remains  for  a 
period  of  time  lying  in  the  beds  and  is  then  led  away  again,  by 
which  means  air  is  sucked  into  the  beds.  With  percolating 
filters  the  sewage  is  continually  percolating  through  the  beds. 
The  size  of  the  pieces  of  material  used  should  be  about  3  to  8 
millimetres  (-^th  to  Jrd  in.)  in  the  case  of  contact  beds,  whilst 
with  percolating  filters  it  is  considerably  larger,  amounting  to  15 
to  75  millimetres  (•£  to  3  in.),  and  there  are  even  larger  in  use 
(Schiele).  With  contact  beds  there  are  two  processes,  known 
as  single-contact  and  double-contact  treatment.  In  the  single- 
contact  process  treatment  is  complete  after  leaving  the  bed. 
In  the  double-contact  process  the  sewage  from  the  primary  bed 
is  delivered  to  a  secondary  bed.  The  material  of  a  primary  bed 
is  coarser  in  grain  than  that  of  the  secondary  bed.  Percolating 
filters  are  generally  worked  with  single  contact. 

As  with  septic  tanks,  so  here  the  beds  have  to  be  prepared  for 
the  work  in  order  that  in  course  of  time  they  cease  to  yield 
effluents  capable  of  putrefaction.  The  time  for  this  process  to 
take  place  may  amount  to  some  months.  It  is  generally  shorter 
with  percolating  filters  than  with  contact  beds,  and  depends  on 
the  gradual  formation  of  a  slimy  layer  on  each  piece  in  the  bed,  a 
discussion  on  the  nature  of  which  layer  will  be  detailed  below  (see 
page  89).  Contact  beds  are  so  worked  that  they  are  filled  with 
sewage,  which  is  then  allowed  to  stand  some  time  in  contact 
with  the  beds,  and  then  to  drain  away.  The  sewage  is  generally 
led  on  to  the  contact  beds  from  above,  and  is  drawn  off  from  under- 
neath. After  each  impregnation  contact  beds  must  be  allowed 
to  stand  some  time,  in  order  to  work  up  the  substances  taken 
from  the  sewage.  In  England  good  results  have  been  obtained 
with  the  beds  full  for  two  hours  and  standing  empty  four  hours 
(Schiele).  In  practice  single-contact  beds  can  be  impregnated 
twice  per  day,  double-contact  beds  three  times  daily.  According 


ARTIFICIAL  BIOLOGICAL   METHOD  87 

to  this,  i  cubic  metre  of  single-contact  bed  can  be  treated  with, 
at  most,  0-66  cubic  metre  of  sewage,  double  contact  with  0-5 
cubic  metre  per  day. 

Percolating  niters  can  be  continuously  impregnated  with 
sewage  without  the  purifying  action  falling  off. 

The  beds  are  either  built  in  the  ground  or  on  the  ground.  It  is 
important  for  good  working  that  they  should  be  maintained  at 
uniform  temperature.  They  should  therefore  be  protected  under 
certain  circumstances  against  cold  in  winter. 

Contact  beds  are  generally  rectangular  ;  percolating  niters  are 
either  rectangular,  octagonal,  or  circular  in  shape. 

In  the  case  of  contact  beds  the  water  is  distributed  on  to  the 
beds  in  a  very  simple  manner.  It  takes  place  through  feed 
channels,  perforated  clay,  or  stoneware  pipes,  open,  perforated 
drains,  perforated  gutters,  and  other  devices.  With  contact  beds 
good  uniform  distribution  is  not  by  any  means  so  important  as 
with  percolating  filters.  In  the  case  of  contact  beds  the  main 
concern  is  the  quickest  possible  filling.  They  are  generally  filled 
and  emptied  by  sluices  and  valves  worked  by  hand.  Frequently 
there  are  also  automatic  devices  for  filling  and  emptying.  Uni- 
form distribution  is,  however,  a  matter  of  very  special  importance 
in  the  case  of  percolating  filters.  The  number  of  devices  invented 
to  attain  this  is  almost  legion.  There  are  sprinklers,  movable 
revolving  sprinklers,  stationary  perforated  pipes,  portable 
sprinklers,  etc. 

In  general,  according  to  Schiele,  with  regard  to  distributors 
for  percolating  filters,  the  following  can  be  said  :•  The  system 
employed  must  always  be  adapted  to  local  circumstances.  It  is 
most  suitable  to  carry  out  experiments  beforehand.  In  Birming- 
ham the  following  requirements  were  demanded  of  a  good 
distributor  :— 

(1)  Uniform  distribution,  so  that  each  portion  of  the  surface 
of  the  bed  contains  precisely  the  same  quantity  of  water. 

(2)  Distribution  in  the  form  of  drops. 

(3)  Absolute  control  over  the  distributor. 

(4)  Limited  cost  of  plant. 

(5)  Small  working  expenses. 

(6)  As  few  movable  parts  as  possible. 

(7)  Small  consumption  of  power  in  distribution. 

With   regard   to  the  water-pressure  necessary   for  working, 


88  SEWAGE   DISPOSAL 

fixed  sprinklers  are  at  a  disadvantage  when  compared  with 
the  automatic  revolving  sprinklers.  The  revolving  sprinklers 
are  found  in  English  experience  to  be  limited  to  a  bed  of 
30  metres  diameter,  or  at  the  most  35  metres.  When  they 
are  to  be  worked  mechanically,  large  rectangular  beds  with 
movable  or  fixed  sprinklers  prove  more  useful  and  advan- 
tageous than  circular  beds  with  revolving  sprinklers.  In 
Germany  automatic  revplving  pipe  sprinklers,  with  a  bed  20 
metres  diameter  and  perforations  every  10  millimetres,  have 
proved  the  best  for  withstanding  strong  cold  in  winter.  In 
England  at  the  present  time  stationary  sprinklers,  especially 
the  Fiddian  type,  are  being  increasingly  employed. 

Contact  beds  and  percolating  filters  are  on  the  whole  to  be 
regarded  as  of  equal  value.  Both  have  their  advantages  and 
disadvantages.  The  advantages  of  contact  beds  are  :  Simple 
distribution  of  the  sewage  on  to  the  beds,  small  trouble  due  to 
smell,  no  plague  of  flies,  little  suspended  matter  in  the  discharge  ; 
small  need  for  a  head  of  sewage  on  account  of  the  small  depth  of 
the  bed,  greater  certainty  of  working  in  the  cold  weather.  As 
opposed  to  these  the  main  advantages  of  percolating  filters  are  : 
Greater  mechanical  power  than  with  contact  beds ;  since  the 
beds  can  be  built  higher  smaller  space  is  necessary  ;  coarse- 
grained, cheap  material ;  little  attention.  Whilst  contact  beds 
are  always  gradually  getting  choked  with  sludge,  and  on  this 
account  need  purifying  more  frequently,  percolating  filters  do 
not  get  choked  with  sludge,  or  at  most  with  very  little.  Per- 
colating filters  also  withstand  an  overload  of  sewage  in  rainy 
weather,  since  the  admittance  of  air  is  never  quite  cut  off.  On 
the  contrary,  percolating  filters  always  contain  a  great  deal  of  sus- 
pended matter,  and  the  discharge  must  be  subsequently  freed  from 
this.  In  percolating  filters  small  flies  establish  themselves  in 
extraordinary  numbers.  Especially  is  the  Psychoda  (the  butterfly 
gnat)  to  be  noted.  Further,  smells  are  never  quite  avoided  in  the 
treatment  of  sewage  with  percolating  filters.  After  the  invention 
of  percolating  filters  one  often  heard  the  opinion  expressed  that 
contact  beds  would  soon  disappear.  This  view  has  not  proved 
correct.  For  the  purification  of  sewage  in  large  towns  it  is  true 
that  percolating  filters  have  proved  themselves  superior  to  con- 
tact beds,  since  all  the  above-named  advantages  of  percolating 
filters  mean  cheaper  cost  of  construction  and  of  upkeep.  For 


ARTIFICIAL   BIOLOGICAL   METHOD  89 

the  centralised  clarification  plants  of  towns,  therefore,  percolating 
filters  are  nowadays  generally  erected.  Still,  even  in  the  most 
recent  years  in  England,  in  large  towns  like  Manchester,  contact 
beds  have  been  put  down  and  have  proved  excellent.  They  are 
especially  suitable  where  the  proximity  of  places  of  residence,  as, 
for  example,  with  small  domestic  or  manufacturing  plants, 
compels  one  to  avoid  smell  or  flies. 

As  has  been  already  mentioned,  the  percolating  filter  effluents 
always  contain  large  amounts  of  suspended  matter  which  are 
washed  out  of  the  beds.  These  substances  differ  greatly  from 
those  in  the  raw  sewage,  in  that  they  are  not  capable  of  putre- 
faction. They  impart  to  the  purified  water  an  objectionable 
appearance,  and  would  lead  to  the  deposition  of  sludge  in  the 
river  ;  consequently  percolating  filter  effluents  are  always  sub- 
sequently clarified.  In  England  this  is  frequently  effected  by 
land  irrigation  (i  acre  to  1000  inhabitants).  Generally, 
however,  the  discharges  are  subsequently  treated  in  simple 
sedimentation  tanks  or  wells.  Since  the  sludge  is  no  longer 
capable  of  putrefaction,  it  is  easily  freed  from  water  and  its 
disposal  causes  no  difficulty. 

The  cost  of  sewage  treatment  by  the  biological  process  varies 
greatly.  The  price  of  material  for  the  beds  varies,  accord- 
ing to  Schiele,  from  3  to  12  marks  per  cubic  metre  (2s.  6d.  to 
los.  per  cubic  yard),  whilst  i  cubic  yard  of  .ready  -  prepared 
material  costs  from  5  to  35  shillings.  The  cost  of  the  bed  in 
England  cannot,  as  a  rule,  be  less  than  15  shillings  per  cubic  yard. 

As  to  the  nature  of  biological  purification  of  sewage  there  exist 
two  views.  According  to  one,  which  is  put  forward  by  Baurat- 
Brettschneider  of  Charlottenburg,  and  which  in  its  essentials 
coincides  with  the  so-called  Hampton  doctrine  championed  by 
Travis,  the  whole  so-called  biological  sewage  treatment  consists 
of  nothing  more  than  a  filtration  of  the  organic  filth,  which,  in 
the  main,  would  be  present  in  the  colloidal  form  in  sewage 
(together  with  the  greater  part  of  the  so-called  dissolved  sub- 
stances). This  theory  is  opposed  to  that  of  Dunbar  and  his  pupils, 
according  to  whom  biological  sewage  purification  is  to  be  explained 
in  the  following  manner  :  Each  single  portion  of  the  bed  is 
gradually  covered  with  a  slimy  surface  of  bacteria  and  other 
organisms.  During  impregnation  the  greater  part  of  the  organic 
matter  is  adsorbed  by  this  covering.  The  film  also  adsorbs 


90  SEWAGE   DISPOSAL 

oxygen  in  large  quantities.  With  the  help  of  this  oxygen  and  of 
the  oxygen  otherwise  entering  the  bed,  the  adsorbed  substances 
are  decomposed  by  the  organisms  in  the  intervals  of  rest  between 
each  impregnation.  This  theory  is  supported  by  numerous 
experimental  data,  so  that  there  can  be  no  doubt  as  to  its  truth. 

(ii)  Land  Treatment. 

Treatment  of  sewage  on  the  land  is  the  oldest  form  of  sewage 
treatment.  Within  the  memory  of  man  it  has  always  been  known 
that  the  surface  of  the  earth  was  able  to  remove  the  evil  smell  of 
sewage  and  to  make  polluted  water  pure. 

Two  methods  of  land  treatment  must  be  distinguished,  namely, 
broad  irrigation  or  sewage  farming,  and  the  intermittent  sand 
filtration  of  Frankland. 

(a)  Sewage  Farming. 

Broad  irrigation  or  sewage  farming  was  first  practised  in 
England.  To-day  there  is  still  in  existence  an  irrigation  bed  that 
has  been  in  use  two  hundred  years.  As  is  well  known,  sewage 
contains  a  number  of  substances  which  are  valuable  as  nutri- 
ment for  plants  (nitrogen,  phosphates,  potash).  The  irrigation 
process  makes  use  of  this  fact,  and  on  the  farms  all  kinds  of  useful 
plants  are  grown.  Thus  by  this  method  of  sewage  disposal,  the 
sewage  is  purified  and  use  is  made  of  the  nutritious  substances 
present  in  it. 

In  England  alluvial  soil  is  considered  to  be  the  best  for  sewage 
farming.  Soil  lying  over  high  waters  generally  in  river  valleys, 
or  sandy  loam  over  gravel  or  gravelly  sand,  or  even  gravelly, 
sandy  subsoil  with  light  or  medium  mainsoil  about  40  centimetres 
deep,  are  all  good.  Gravel  without  a  finer  covering  layer  serves 
also  as  regards  permeability  (Schiele).  The  poorest  earth  is  clay, 
loam,  clayey  soil  and  turf.  Clayey  soil,  since  it  is  not  permeable, 
can  only  be  used  for  the  so-called  surface  or  rude  irrigation. 

According  to  Dunbar,  there  are  two  main  kinds  of  irrigation 
processes.  In  the  first  kind  the  water  flows  down  from  the  highest 
point  of  the  land.  After  trickling  over  the  surface  of  one  field 
it  is  collected  into  a  ditch,  from  which  it  is  again  uniformly  dis- 
tributed over  the  next  field.  With  a  sharply  inclined  tract  of 
land,  dams  must  be  thrown  up  to  retard  the  flow  of  the  sewage 


LAND   TREATMENT  91 

and  to  distribute  it  afresh.  When  the  track  is  not  so  steep  the 
operation  is  carried  out  in  the  following  manner:  The  sewage 
flows  from  the  distributors,  passing  transversely  from  the  irriga- 
tion plant  into  smaller  trenches  arranged  perpendicularly  to  the 
larger.  These  are  dammed  up  at  the  ends  so  that  the  sewage 
must  overflow  from  the  trenches  at  the  sides.  It  then  flows  over 
the  sloping  surfaces  of  meadow  into  lower  lying  ditches.  Then 
from  these  second  distributing  ditches,  in  precisely  the  same 
manner,  the  water  is  again  distributed  over  a  second  series  of 
meadows.  This  process  is  generally  used  for  surface  irrigation 
only,  and  in  those  cases  where  the  land  lies  so  low  that  it  cannot 
be  drained.  A  good  drainage  is  not  usual,  therefore,  with  the  plant. 

In  Germany  and  also  in  France,  as  far  as  possible,  it  is  en- 
deavoured to  lay  out  sewage  farms  on  the  principle  known  as  bed 
irrigation.  In  this  process  surface  treatment  with  sewage  is  done 
away  with,  as  the  water  passes  through  the  ground.  It  is  therefore 
true  irrigation.  The  sewage  is  led  on  to  the  farm  in  ditches. 
The  distributing  canals  are  only  allowed  to  fill  so  far  with  sewage 
that  this  has  to  pass  into  the  bed  sideways  and  below  the  surface. 
Wetting  the  stems  and  leaves  of  the  plants  is  thus  avoided.  The 
beds  are  usually  only  i  metre  broad  by  20  to  40  metres  long,  as 
otherwise  uniform  distribution  of  the  sewage  cannot  be  attained. 
In  this  process  many  distributing  ditches  are  required,  and  also 
paths  from  which  the  beds  can  be  attended  to.  This  means, 
therefore,  considerable  loss  in  working  space. 

Further,  a  process  may  also  be  briefly  described  here  which, 
up  to  the  present,  has  not  been  widely  employed,  but  which 
might  render  good  service  in  those  places  where  no  suitable  land 
for  sewage  farming  is  to  be  had  in  the  neighbourhood  of  towns 
and  manufactories.  The  method  consists  in  conducting  the 
sewage  to  farms,  and  here  by  means  of  hoses  it  is  squirted  on  to 
the  fields.  In  the  year  1897  it  was  first  used  by  Nobel  in  Eduards- 
feld,  near  Posen,  with  5j  million  gallons  of  sewage  yearly  from 
the  town  of  Posen.  The  process  is  named  after  the  inventor,  and 
is  known  as  "  Benobelung "  (The  Nobel  Treatment),  or  the 
Eduardsfeld  process,  and  also  as  hose  irrigation. 

In  most  cases  the  subsoil  is  drained.  The  purified  sewage  is 
conveyed  to  the  river  in  collecting  ditches.  Under  loam  or  clayey 
soils  drainage  is  naturally  not  effected,  since  it  would  serve  no 
purpose.  The  action  in  sewage  farming  is  first  of  all  a  filtration 


92  SEWAGE    DISPOSAL 

process,  since  all  suspended  matter  exceeding  in  size  the  pores 
of  the  ground  is  retained.  Further,  a  large  number  of  bacteria 
are  removed.  Then  again,  in  a  manner  similar  to  that  occurring 
with  contact  beds  and  percolating  filters,  but  still  more  pro- 
nouncedly, dissolved  organic  matter  is  decomposed  by  the  aid  of 
micro-organisms  in  the  ground.  The  sewage  flowing  away  in  the 
effluent  drains  differs  from  the  raw  sewage  in  that  it  is  quite  clear 
and  no  longer  capable  of  putrefaction.  It  contains  considerably 
less  oxidisable  matter,  and  the  nitrogen  compounds  are  to  a  great 
extent  removed  and  converted  in  part  to  nitrous  and  nitric  acids. 

The  action  in  surface  irrigation  is  not  so  effective  as  that  in 
true  irrigation. 

In  all  circumstances  purification  of  the  sewage  before  disposal 
on  the  farm  is  to  be  recommended.  If  this  be  done  larger  amounts 
of  sewage  can  be  disposed  on  the  surface.  In  this  preliminary 
purification  there  come  into  consideration  screens,  grit  chambers, 
and  septic  tanks,  as  well  as  sedimentation  processes  with  or 
without  chemical  precipitation.  Indeed,  in  certain  cases  the 
sewage  is  treated  in  contact  beds  or  percolating  niters  before 
disposal  on  the  farm. 

With  good  management  the  purifying  action  of  sewage  beds 
is  quite  unlimited.  Bad  working  is  generally  attributable  to 
false  application  of  principles,  or  to  errors  in  the  original  plant. 
Corn  and  potatoes  are  not  suitable  products  to  cultivate  in  the 
view  of  English  authorities  (Schiele)  ;  on  the  contrary,  grass, 
carrots,  and  cabbages  are  very  suitable.  As  regards  pasturage 
opinion  is  divided. 

The  main  purpose  of  sewage  farms  must  always  be  sewage 
purification ;  the  yield  of  the  process  must  not  be  increased  at 
the  expense  of  good  purification.  It  is  inadvisable  on  this  account 
for  towns  to  lease  their  sewage  farms  to  farmers,  as  the  latter 
have  always  got  the  profit  uppermost  in  their  minds.  Large 
sewage  farms  can,  as  a  general  rule,  be  better  and  more  rationally 
arranged  than  smaller  ones.  In  England,  therefore,  small 
municipalities  are  advised  rather  to  join  with  several  others  in 
order  to  set  up  a  joint  sewage  farm  than  to  erect  several  small 
plants.  There  are  no  scruples  in  England  against  keeping  cattle 
on  sewage  farms. 

Heavy  rainfall  has  naturally  a  very  deleterious  influence  on 
the  capacity  of  a  sewage  farm  to  take  up  the  sewage. 


LAND   TREATMENT 


93 


On  the  whole,  according  to  Schiele,  sewage  farms  can  be 
regarded  as  percolating  niters.  The  fineness  of  grain  demands 
similar  treatment  to  that  with  contact  beds,  viz.  they  must  have 
periodical  rests.  The  sewage  farm  must  consequently  be  chosen 
so  large  that  a  portion  of  it  can  always  remain  unemployed. 
The  last  English  Royal  Commission  on  Sewage  Disposal  con- 
cluded that  the  most  useful  ratio  of  working  surface  to  surface 
unemployed  was  in  the  case  of  surface  irrigation  1:5,  and  for 
true  irrigation  1:3.  The  same  Royal  Commission  has  placed  in 
Volume  IV  of  their  Proceedings  the  results  of  searching  experi- 
ments on  the  land  treatment  of  sewage.  Thereby  the  following 
figures,  per  unit  of  land,  are  obtained  as  admissible  amounts  of 
sewage  which  has  undergone  preliminary  mechanical  or  chemical 
treatment  : — 


At  a  g-iven  time  per           On  year's  working-  over 

24  hours. 

whole  area. 

Inhabitants 

Soil. 

Gallons 
per  acre. 

(calc.  at  40 
gal.  per  head 
per  acre 

Gallons 
per  acre. 

Inhabitants. 

per  day),     i 

1 

Best  kind  for 
filter  purposes 
(light  sandy 
loam  overlay- 
ing- gravel  and 
sand). 

23,000 
(strong- 
mixed  sew- 
age). 
100,000 
(rather  weak 
sewage). 

600 
2500 

Over 

10,000 

30,000 
(rather 
weak  ). 

250 
750 

Soil  less  well 

suited  (sand 
and  partially 
peaty  soil  lying 
upon  sand  and 

25,000 
to 
46,000 

600 
to 
1150 

8000 
to 
23,000 

200 

to 

600 

Domestic 
sewage 
(weak). 

gravel). 

. 

Bad  soils 
(from  gravelly 
loam  to  heavy 
loam  or  clay). 

12,000 

to 
57,000 

300 
to 
1400 

4000 
to 
9000 

IOO 

to 

225 

Combined 
surface  irri- 
gation and 
filter  farms. 

Rents  of  sewage  farms  vary  considerably.  Whilst  many  sewage 
farms  lose  large  sums  of  money,  others  not  only  pay  for  the  total 
cost  of  working,  but  even  create  a  surplus.  This  is  explained  on 
the  grounds  that  the  original  outlay,  especially  the  cost  of  obtaining 


94  SEWAGE   DISPOSAL 

land,  shows  great  differences.  Further,  it  must  be  borne  in 
mind  that  sewage  farms  making  a  profit  are  generally  the  leased 
farms,  in  which  case,  as  already  mentioned,  purification  is  often 
insufficient,  as  the  profit  is  the  primary  consideration  of  the 
management. 

The  cost  of  sewage  farming,  apart  from  surpluses,  amounts, 
according  to  Fruhling,  to  i-2d.  in  Berlin,  o«37d.  in  Breslau, 
o-87d.  in  Brunswick,  o-25d.  in  Magdeburg,  o-8id.  in  Dortmund, 
and  o-3gd.  in  Freiburg  per  1000  gallons  of  purified  sewage. 


(b)  Intermittent  Sand  Filtration,  according  to  Frankland. 

In  the  year  1871  Frankland  showed  that  domestic  sewage 
could  be  effectively  purified  by  irrigation  if  it  were  filtered  through 
a  sufficiently  large  layer  of  sand.  Choking  of  the  filter  could  be 
avoided  if  the  sewage  were  not  conveyed  to  the  filter  uninter- 
ruptedly, that  is,  if  after  each  impregnation  an  interval  of  rest 
were  allowed  to  ensue.  The  sludge  abstracted  is  then  decomposed 
by  organisms  as  in  contact  beds,  percolating  filters,  and  sewage 
farms.  It  was  on  account  of  these  periods  of  rest  that  Frankland 
named  his  process  "  Intermittent  Sand  Filtration." 

Intermittent  sand  filtration  differs  from  irrigation  processes 
chiefly  in  this,  that  filtration  is  effected  in  specially  prepared  beds 
of  sand  which  can  be  dosed  with  far  more  sewage  than  sewage 
farms  with  equally  effective  purification.  The  portions  of  the 
sewage  valuable  as  plant  nutriment  cannot  however  be  utilised 
agriculturally,  and  so  cultivation  of  the  surface  must  be  sacrificed. 

The  method  was  first  used  most  frequently  in  England.  It 
was  badly  managed,  and  gave  rise  to  various  troubles  such  as 
stoppages  in  the  sand,  evil  smells,  and  the  like,  with  the  result 
that  the  process  was  for  a  long  time  discredited. 

Then  the  State  of  Massachusetts,  U.S.A.,  demonstrated  the 
value  of  the  process  by  means  of  searching  experimental  work, 
using  an  experimental  plant  at  Lawrence,  and  with  large  plants 
based  upon  this.  They  established,  as  a  consequence,  the  good 
repute  which  the  process  to-day  enjoys. 

Henneking  studied  the  plant  closely  in  the  State  of  Massa- 
chusetts, and  reported  in  the  "  Mitteilungen  der  Konigl.  Prii- 
fungsanstalt  fur  Wasserversorgung  und  Abwasserbeseitigung  " 


LAND   TREATMENT  95 

(Proceedings  of  the  Royal  Test  Institute  for  Water  Supply  and 
Sewage  Disposal)  upon  his  own  observations  on  the  spot  and  on 
the  results  obtained.  The  practical  knowledge  gained  during 
more  than  eighteen  years  in  Massachusetts  shows  that  with  the 
conditions  present  there  it  is  most  suitable  not  to  submit  the 
sewage  to  preliminary  treatment  before  disposal  on  the  filter-beds. 
American  sewage  is  always  thin,  about  half  as  thin  as  mean 
German  domestic  sewage.1  It  also  contains  no  noteworthy 
amounts  of  industrial  effluents.  Purification  is  more  complete 
the  sooner  the  sewage  is  conveyed  to  the  filter-bed.  Suspended 
matter  is  retained  on  the  surface  of  the  bed,  and  can  be  scraped 
off  in  a  cheap  and  convenient  manner  after  it  has  sufficiently 
dried.  In  this  process,  for  an  unlimited  number  of  years  good 
purification  continually  results  with  doses  of  40,000  to  80,000 
gallons  per  acre.  The  amount  of  impregnation  within  these 
limits  is  adjusted  according  to  the  concentration  and  compo- 
sition of  the  sewage  on  the  one  hand,  and  to  the  nature  of  the 
filtering  medium  on  the  other. 

The  most  suitable  soil  for  the  filter-bed  is  one  free  from  organic 
matter,  porous  sand,  and  gravel  of  0-04  to  075  millimetre  size 
of  grain.  It  should  be  of  uniform  nature  throughout ;  that  is  to 
say,  the  whole  bed  must  contain  per  unit  volume  approximately 
the  same  number  of  sand  grains  of  various  sizes.  Loamy  surface 
layers  and  intermediate  layers  must  be  removed.  The  surface 
of  the  filter  must  be  horizontal,  or  possess  a  slight  inclination  of 
i  :  200  to  i  :  500.  The  depth  of  the  filter  layer  should  be  at 
least  4  to  5  feet  on  an  average.  The  main  purification  of  the 
sewage  is  accomplished  in  the  upper  layer  to  a  depth  of  2  to 
3  feet.  A  rectangular  bed  about  i  acre  area  has  proved  the 
most  suitable  arrangement.  The  beds  must  be  well  drained 
so  that  the  treated  sewage  can  flow  away  easily.  It  is  distinctly 
worth  while  striving  to  design  the  drainage  on  the  separate 
system  (Trenn  system). 

Subsequent  treatment  of  the  purified  sewage  is  unnecessary. 

The  periods  of  rest  given  after  each  application  vary  con- 
siderably. They  vary  between  several  hours  and  three  days,  and 
generally  last  about  24  hours,  so  that  the  filter  can  be  dosed  once 
a  day.  Since,  as  already  mentioned,  the  filter-beds  are  much 

1  English  sewage  of  mean  concentration  is  regarded  as  thin  for  German  work- 
ing conditions. — Trans. 


96  SEWAGE   DISPOSAL 

more  heavily  charged  with  sewage  than  in  the  case  of  sewage 
farms,  expense  is  considerably  less  with  intermittent  sand 
nitration.  That  is  to  say,  whilst  an  acre  of  filter-beds  can  be 
treated  with  the  sewage  of  1250  persons  daily,  an  acre  of  sewage 
farm  can  only  purify  sewage  from  no  persons.  Intermittent 
filtration  therefore  only  requires  about  one-eleventh  of  the  total 
surface  necessary  for  sewage  farming.  The  cost  of  intermittent 
sand  filtration  fluctuates  correspondingly  between  o-O4d.  and 
i'34d.  per  1000  gallons  of  sewage,  and,  according  to  Hen- 
neking,  should  only  amount  to  8-2  per  cent  of  the  cost  in  sewage 
farming.  The  purifying  action  of  the  sand  filter  is  never  so 
complete  as  that  occurring  in  broad  irrigation.  In  Germany  the 
process  has  not  come  into  practical  application  up  to  the  present. 


(iii)  Sewage  Purification  by  means  of  Fish-ponds. 

Frequently  it  has  been  proposed  to  purify  sewage  by  con- 
veying it  to  fish-ponds.  The  putrefactive  matter  decomposes 
there  in  agreement  with  the  observations  made  in  the  section  on 
"  Self-purification  of  Rivers  "  by  various  organisms,  of  which  the 
larger  always  prey  upon  the  smaller.  The  organic  matter  intro- 
duced with  the  sewage  is  thereby  converted  into  fish  tissues. 
Naturally,  therefore,  the  sewage  must  be  so  diluted  that,  in  the 
first  place,  direct  harm  to  the  fish  is  avoided,  and  secondly,  that 
purification  can  proceed  normally.  In  the  former  case  with  too 
high  concentrations  of  sewage,  sulphuretted  hydrogen  and  other 
inimical  substances  cause  damage. 

Cronheim  carried  out  experiments  in  this  direction  which 
demonstrated  the  important  fact  that  fish  requiring  little  oxygen, 
like  carp  and  tench,  withstood  an  introduction  of  sewage  to  the 
extent  of  10  per  cent  of  the  total  volume  of  the  pond.  Decom- 
position did  not  occur  in  the  water,  nor  did  sludge  collect  on  the 
bottom  of  the  pond. 

In  later  experiments  Cronheim  introduced  10  per  cent  of 
sewage  every  4  to  8  days  into  a  pond  which,  besides  carp  and 
tench,  also  contained  trout  and  perch.  In  these  experiments 
also,  with  fish  needing  oxygen  in  high  degree  like  trout,  no  harm 
resulted.  Whilst  an  acre  of  sewage  farm  can  only  absorb  the 
sewage  of  100  people,  a  pond  containing  carp,  of  half  an  acre  area 


RESIDUES  97 

should,  according  to  Hofer,  continuously  absorb  the  sewage  of 
300  persons  without  extensive  decomposition  setting  in.  This 
method  is  especially  suitable  for  flat  land,  single  farms,  hospitals, 
etc.,  but  Hofer  also  maintains  that  it  is  applicable  to  large  towns 
like  Munich. 

According  to  Schick,  the  method  is  employed  with  the  best 
results  for  the  Kreisirrenanstalt,  Kutzenberg  in  Oberfranken 
(300  persons),  with  a  pond  0-5  acre  in  area.  At  Bau  the  same 
author  points  out  that  there  should  shortly  be  plants  for  the 
South  Bavarian  townships  of  Weinding  and  Ichenhausen  with 
about  3000  inhabitants.  Further  experience  with  regard  to 
expense  and  management  must  be  awaited. 


IV.    THE    DISPOSAL    OF    SEWAGE    RESIDUES    AND 
THEIR    VALUE. 

(i)  Residues  from  Grit  Chambers  and  Screens. 
Sludge  from  Sedimentation  Tanks. 

The  residues  resulting  from  sewage  treatment  are  grit-chamber 
residues,  residues  from  screens,  the  sludge  from  sedimentation 
tanks,  and  the  sludge  from  the  plants  for  purification  of  the 
effluents  from  percolating  filters.  With  the  exception  of  the  last 
they  are  all  more  or  less  capable  of  putrefaction.  The  disposal  of 
sludge  is  the  most  difficult  and  most  important  question  in  sewage 
disposal.  A  solution  of  the  sludge  problem  that  is  satisfactory 
in  every  case  is  not  yet  known. 

The  residues  from  grit  chambers  and  screens  are  not  large  in 
amount.  Generally  not  more  than  15  to  20  per  cent  of  the  un- 
dissolved  substances  present  in  the  sewage  is  displaced  in  these 
purification  processes.  Grit-chamber  residues  mainly  consist  of 
sand,  rags,  bones,  coffee  grains,  and  similar  substances.  They 
usually  contain  60  to  70  per  cent  of  water.  The  dried  material 
generally  consists  of  two-thirds  mineral  and  one-third  organic 
matter.  In  Frankfort,  with  about  400,000  inhabitants  and 
22,000,000  gallons  dry-weather  flow  per  day,  approximately 
350  to  550  cubic  feet  of  grit-chamber  residues  are  obtained  in 
24  hours.  Its  disposal  generally  occasions  no  great  difficulty. 
The  material  is  quite  firm  when  it  contains  60  to  70  per  cent  of 


98  SEWAGE   DISPOSAL 

water.  It  is  dried  by  being  laid  on  level  ground.  No  great  area 
is  needed  for  this  storage  ;  and  it  dries  fairly  quickly.  The  dried 
residues  are  sold  to  farmers  as  manure.  The  Frankfort  grit- 
chamber  residues  contain  about  0-12  per  cent  N,  i-oi  per  cent 
phosphoric  acid  (P2O6),  and  0-12  per  cent  potash  (K2O)  in  the 
dried  substance.  The  residues  accumulating  every  day  from  a 
fine  screening  plant  are  about  as  considerable  as  those  from  grit 
chambers.  They  consist  mainly  of  excreta  and  paper.  They 
contain  about  80  per  cent  of  water.  The  dried  substance  consists 
almost  entirely  of  organic  matter.  They  also  are  stored,  dried 
in  the  air,  and  are  sold  either  wet  or  dry  as  manure.  Although 
these  residues  do  not  occupy  much  room  in  their  storage,  still,  on 
account  of  the  faeces  they  contain,  and  the  consequent  offensive 
smell,  they  may  be  very  disagreeable.  Residues  from  the  Frank- 
fort screens  contain,  when  dry,  about  0-82  per  cent  N,  1-57  per 
cent  P2O5,  and  0-40  per  cent  potash  (K2O). 

By  far  the  most  important  portion  of  the  residue  accumulating 
is  the  sludge  from  the  sedimentation  tanks.  It  settles  to  the 
bottom  of  the  tanks,  wells,  etc.,  in  the  sedimentation  process  and 
forms  a  continually  decomposing  black  mass  which  is  of  pulpy 
or  watery  consistency,  always  evolving  an  extremely  offensive 
smell.  The  sludge  consists  mainly  of  triturated  faeces,  paper 
fibre,  coffee  dregs,  sand,  etc.  Its  black  colour  arises  from  small 
quantities  of  sulphide  of  iron,  formed  by  the  interaction  of  the 
sulphuretted  hydrogen  resulting  from  the  fermentation  in  the 
sludge  with  the  iron  salts  present  in  the  sewage.  It  generally 
contains  90  to  95  per  cent  water.  The  composition  of  the  dried 
substance  depends  upon  the  local  circumstances  and  the  sedi- 
mentation process  employed.  Sludge  separated  mechanically 
and  without  the  addition  of  chemicals  contains,  in  the  dried 
material,  about  50  per  cent  organic  and  50  per  cent  mineral 
matter.  It  further  contains,  in  substances  of  nutritive  value  to 
plants,  approximately  2  to  3  per  cent  N,  about  the  same  amount 
of  phosphoric  acid  (P2O5),  and  about  0-5  per  cent  potash  (K2O) 
in  the  dry  substance.  The  high  grease  content  of  the  sludge 
from  sedimentation  tanks  is  noteworthy.  Frankfort  sedimenta- 
tion sludge  contains  on  an  average  about  18  per  cent  grease  in 
the  dried  substance.  This  grease  arises  in  part  from  the  grease 
of  factories,  cooking  refuse,  and  faeces,  mainly,  however,  from  the 
soap  used  in  washing.  The  alkali  soaps  are  decomposed  by  the 


DRYING   THE   SLUDGE  99 

lime  salts  in  the  sewage  and  yield  insoluble  lime  soaps,  which  are 
precipitated  in  flakes  and  settle  to  the  bottom  of  the  tanks  or 
wells  in  the  sedimentation  process.  The  grease,  which  is  separated 
from  the  sludge  by  slightly  acidifying  with  sulphuric  acid,  has 
the  following  composition  :  68  to  73  per  cent  free  fatty  acids 
coming  from  the  soaps  ;  18  to  20  per  cent  neutral  fats  (faeces, 
fat,  grease  from  cooking  effluents)  ;  7  to  14  per  cent  unsaponifi- 
able  portion  (lubricating  oils).  It  can  readily  be  understood 
that  these  numbers  may  be  very  different  with  sludge  from  a 
sedimentation  plant  which  works  up  large  amounts  of  industrial 
effluents,  as  is  the  case  in  Frankfort. 

The  chief  difficulty  in  sludge  disposal  is  the  large  amount  of 
water  it  contains.  Since  this  amounts  to  90  per  cent  or  more,  it 
not  only  occupies  very  valuable  space,  but  also  the  large  amount 
of  water  offers  to  anaerobic  or  putrefactive  fungi  of  the  most 
varied  kinds  a  nutritive  substrate  which  very  quickly  assumes 
a  foul  and  stinking  condition. 

The  whole  problem  of  sludge  disposal  is  the  removal  of  the 
water. 

(ii)  Drying  the  Sludge. 

The  most  widely  disseminated  process,  and  the  one  longest  in 
use  for  drying  sludge,  is  to  spread  it  on  the  land.  A  part  of  the 
water  thereby  drains  away  into  the  ground  and  another  portion 
evaporates.  The  removal  of  water  takes  place  very  slowly, 
however,  on  account  of  the  slimy  nature  of  the  sludge.  Months 
and  years  go  by  before  the  sludge  is  dry.  The  consequence  is 
that  the  place  where  sludge  is  stored  is  very  noticeable,  especially 
in  warm  years,  on  account  of  its  extremely  disagreeable  smell. 
The  gas  arising  during  the  fermenting  process  from  the  sludge  is 
combated  by  covering  the  sludge  with  some  protecting  material 
like  turf,  tar,  etc.,  or  decomposition  is  checked  by  covering  the 
uppermost  layer  with  disinfectants  (saprol,  tar,  chloride  of  lime, 
etc.).  As  too  deep  a  layer  of  sludge  cannot  be  deposited  on  the 
storage-ground  if  it  is  not  to  take  too  long  to  dry,  the  storage  of 
sludge  becomes  rather  costly,  as  considerable  expenditure  is 
entailed  in  purchasing  land.  Fresh  sludge  from  sedimentation 
tanks  and  wells  shows  all  these  unacceptable  features  when 
spread  out  on  the  land,  but  septic-tank  sludge  has  much  more 
favourable  properties.  It  has  a  higher  percentage  of  dry  sub- 


100  SEWAGE   DISPOSAL 

stance  than  fresh  sludge,  its  smell  is  less  offensive,  but,  above  all, 
it  gives  up  its  water  much  more  readily  when  brought  on  to  the 
soil. 

According  to  Spillner,  Emscher-well  sludge  should  have  all  the 
good  properties  of  septic-tank  sludge.  It  contains  considerably 
less  water  than  sludge  from  septic  tanks.  With  70  per  cent  water 
it  is  pulpy  and  quite  mobile,  and  it  has  no  offensive  odour. 
Spillner  carried  out  parallel  experiments  on  the  removal  of  water 
from  fresh  and  from  Emscher-well  sludge.  The  experiments 
showed  that  the  fresh  sludge  needs  a  much  longer  time  to  reach 
firm  consistency  than  does  the  sludge  which  has  been  liquefied, 
and  also  that  fresh  sludge  gives  up  much  less  drain-water  than  the 
liquefied  sludge. 

The  favourable  results  obtained  with  liquefied  sludge  are  due, 
according  to  Spillner  and  Imhoff,  to  the  higher  content  of  dry 
substance  which  septic -tank  sludge  possesses,  to  the  greater 
amount  of  gas  which  partially  putrefied  sludge  contains,  and  to 
the  fact  that  in  such  sludge  the  colloids,  which  are  the  main  cause 
of  the  tenacity  with  which  the  water  is  held,  are  destroyed 
during  the  decomposition  process. 

Sludge-drying  by  drainage  is  carried  out  on  a  large  scale  with 
Emscher  wells  in  the  plants  at  Essen,  N.W.,  Bockum,  and 
Recklinghausen-Ost.  The  results,  so  Spillner  reports,  are  as  yet 
very  favourable. 

A  drying  process  employed  in  England  consists  in  bringing  the 
sludge  into  a  freshly  Opened  ditch.  The  water  is  drawn  out  more 
quickly  by  the  loosened  soil.  As  soon  as  the  sludge  is  so  dry  that 
it  can  bear  the  soil  which  has  been  dug  out,  the  latter  is  filled  in. 
With  sludge  from  sedimentation  tanks  the  drying  is  still  a  very 
wearisome  process. 

In  Gottingen  and  Kassel  the  sludge  is  compounded  with  refuse. 

It  is  readily  understandable  that  efforts  have  frequently  been 
made  to  replace  the  method  of  drying  sludge  on  the  land  by  a 
process  permitting  quicker  drying.  Filtration  is  the  most 
important  of  the  methods  considered.  It  has  given  poor  results 
in  many  localities.  The  colloids  in  the  sludge  render  the  removal 
of  water  by  filter-presses  impossible,  since  they  very  soon  choke 
up  the  filter  fabric.  If  the  mud  be  expressed  when  hot,  or  chemicals 
be  added,  the  results  obtained  are  better,  but  the  process  then 
becomes  very  expensive.  To  the  knowledge  of  the  author  filter- 


DRYING   THE   SLUDGE  101 

presses  are  on  this  account  never  used  in  Germany.  In  England, 
nevertheless,  they  are  not  infrequently  used  for  removing  water 
from  sludge.  In  these  cases  the  sludge  is  obtained  in  sedimenta- 
tion processes  in  which  chemicals  are  employed,  and  therefore 
contains  considerable  amounts  of  lime. 

Much  better  results  have  been  aimed  at  in  recent  times  by  the 
use  of  centrifuges.  At  Frankfort -on -Maine,  Harburg,  and 
Hanover  the  sludge  from  the  sedimentation  processes  is  freed 
from  water  by  centrifuges  of  the  Schafer-ter-Mer  type.  This 
apparatus  is,  mechanically  and  hygienically,  the  most  perfect 
apparatus  designed  for  the  removal  of  sludge  by  the  aid  of 
centrifuges.  It  works  perfectly  automatically,  and  the  workmen 
do  not  come  into  contact  with  the  residues  at  all  (Figs.  20  and  21). 
The  sludge  flows  from  the  feed  reservoir  through  a  vertical  rotary 
axle  and  into  the  centrifuge  in  such  a  way  that  it  is  distributed 
into  six  presses  arranged  radially  to  the  axle,  and  separate  one 
from  another.  These  presses  or  compartments  are  divided  by 
vertically  placed  sieves  into  a  sludge  space  and  sewage  space. 
The  sludge  enters  the  sludge  portion,  in  which  the  coarser 
particles  are  whirled  to  the  outside  by  centrifugal  force  (about 
750  revolutions  per  minute),  whilst  the  sewage  is  conveyed 
through  the  sieves  into  the  neighbouring  sewage  space.  The 
sieves  are  prevented  from  choking  by  an  automatic  cleaning 
device.  When  the  centrifuge  has  been  working  from  one  to  two 
minutes  the  sludge  chambers  are  completely  filled.  The  sludge 
supply  is  then  automatically  cut  off  by  a  circular  disc.  Imme- 
diately subsequent  to  this  another  circular  disc  opens  which 
serves  to  close  the  presses  usually,  and  through  the  opening  so 
obtained  the  centrifuged  sludge  is  hurled  out  of  the  presses. 
After  the  disc  has  automatically  closed  the  press,  the  disc  at  the 
sludge  inlet  opens,  and  the  process  is  repeated.  The  machine 
works  without  any  stoppages.  The  opening  and  closing  of  the 
discs  is  automatically  set  working  by  oil-pressure  with  the  help  of 
a  certain  mechanism.  The  machine  requires  no  attention  apart 
from  the  removal  of  the  oil.  The  cost  is  rather  considerable  ; 
it  amounts,  according  to  Reichler  and  Thiesing,  to  i  shilling 
per  10  cubic  feet  of  dried  sludge,  whilst  removal  of  water  by 
filter-presses  should  only  amount  to  8d.  A  further  disad- 
vantage of  the  process  is  that  the  sewage  flowing  out  of  the 
centrifuge  still  contains  a  large  quantity  of  solid  substances. 


102 


SEWAGE   DISPOSAL 


This  disadvantage,  however,  does  not   alter  the  fact  that   the 
method  is  at  the  present  time  the  only  one  permitting  rapid 
removal  of  water  from  sludge  in  a  relatively  simple  manner,  and 
one  free  from  objection  from  the  point  of  view  of  hygiene. 
In   Frankfort,   experiments  carried  out   on   a  small  scale  to 


FIG.  20.     CENTRIFUGE  FOR  SLUDGE  :   SCHAFER-TER-MER  SYSTEM. 

remove  water  by  an  electro-osmotic  process  have  not  yet  been 
tested  on  a  large  scale. 

Towns  near  the  sea  often  get  rid  of  sludge  in  the  handiest  way 
by  sinking  it  in  the  sea.  Though  the  method  is  one  of  the  cheap- 
est, it  is  not  so  cheap  as  might  at  first  be  believed,  for  sludge 
vessels  must  proceed  a  good  way  out  to  sea  if  the  tide  is  not  to 
throw  up  the  sludge  on  the  shore.  According  to  Spillner,  the 


DRYING   THE    SLUDGE 


103 


method  is  employed,  among  others,  in  London,  Manchester,  and 
Salford,  and  it  is  proposed  for  many  other  localities,  e.g.  Belfast. 
London  possesses  a  whole  fleet  of  sludge  vessels,  each  of  which  holds 
1000  tons  and  costs  £30,000,  not  to  mention  the  large  iron 


Inlet  of  the  y 
Raw  Wate 


FIG.  21.     CENTRIFUGE  FOR  SLUDGE  :   SCHAFER-TER-MER  SYSTEM. 

tanks  on  the  plant  in  which  the  sludge  is  stored  prior  to  the  arrival 
of  the  vessels.  The  London  vessels  take  the  sludge  sixty-five 
miles  out  to  sea,  while  Manchester  and  Salford  have  a  ship  which 
goes  fifty  miles  out  to  sea.  On  an  average  three  journeys  are 
made  per  week. 


104  SEWAGE   DISPOSAL 

Weldert  reports  in  a  preliminary  communication  that  by 
adding  saltpetre,  sludge  from  sedimentation  tanks,  as  well  as 
sewage,  loses  its  capacity  to  putrefy.  As  the  foul  nature  of 
sludge  is  one  of  its  greatest  nuisances,  it  may  be  possible  to  treat 
it  with  nitrates  and  then  dry  it  in  the  air. 

The  costs  of  the  various  methods  of  sludge  disposal  are  given 
by  the  last  English  Royal  Commission  on  Sewage  Disposal  as 
follows  : — 

Land  treatment    About  2d. 

Sinking  in  the  sea ,,    5d. 

Digging  into  trenches    ,,    5d. 

Filter-presses    ,,    6d.  to  is- 

Presses  and  combustion ,,    is.  6d. 

(estimated) 

per  ton  of  aqueous  sludge  containing  about  90  per  cent  of  water, 
inclusive  of  interest  on  plant  capital  and  all  expenses,  charges, 
and  taxes,  without  reference  to  the  value  of  the  sludge  as  manure 
or  to  its  calorific  value. 

(iii)  Profit  from  Sludge. 

To  cover  at  least  a  portion  of  the  expense  incurred,  attempts 
are  continually  being  made  to  realise  a  profit  from  the  disposal 
of  sludge. 

Sale  for  agricultural  manuring  purposes  is  the  method  which 
has  been  used  most  frequently.  As  has  been  already  pointed  out, 
sludge  contains  in  no  inconsiderable  amount  substances  nutri- 
tious to  plants,  especially  nitrogen  (generally  2  to  3  per  cent  in 
the  dried  material). 

Wet  sludge,  from  which  no  water  has  been  removed,  is  only 
employed  as  manure  in  those  places  where  there  is  agricultural 
work  in  the  neighbourhood  of  the  sewage  plant  to  which  it  can 
be  delivered.  Damp  sludge  could  not  bear  the  cost  of  carriage 
to  greater  distances,  as  its  manurial  value  would  not  be  in  any 
way  proportional  to  this  cost,  apart  altogether  from  the  con- 
sideration that  it  would  not  be  practicable,  on  account  of  the 
nuisance  due  to  smell.  In  Frankfort,  till  recently,  the  fresh  sludge 
was,  in  part,  directly  sprinkled  over  the  fields  in  adjacent  agri- 
cultural undertakings.  For  this  purpose  long  pipes  were  laid 
to  which  movable  pipes  could  be  attached. 


PROFIT  FROM   SLUDGE  105 

Frequently  experiments  have  been  carried  out  with  a  view  to 
further  drying  the  sludge  which  had  previously  been  freed  from 
a  portion  of  its  water  by  the  above-mentioned  methods,  and  with 
a  view  to  selling  the  dried  product  as  poudrette  (artificial  manure). 
Ten  years  ago  in  Frankfort  such  a  plant  was  worked.  The  sludge 
was  freed  from  water  on  the  storage-grounds  until  quite  firm,  and 
was  then  dried  further  in  a  drying  plant  until  it  contained  10  to 
20  per  cent  wrater.  The  "  poudrette  "  thus  obtained  contained 
about  17  per  cent  nitrogen  and  2  per  cent  phosphorip  acid.  The 
residue  in  nitrogen  as  compared  with  the  above-mentioned 
numbers,  shows  clearly  that  part  of  the  nitrogen  is  present  in  the 
form  of  ammonia  which  volatilises  on  drying.  The  method  was 
a  failure,  since  a  hundredweight  of  dried  poudrette  cost  about 
a  shilling.  Similar  results  have  been  obtained  in  towns  that 
have  tried  to  prepare  artificial  manure  from  sludge,  so  that  this 
method  of  making  a  profit  can  now  be  considered  non-existent. 

The  large  amount  of  grease  in  sludge  from  sedimentation  pro- 
cesses has  over  and  over  again  provided  an  inducement  for  deter- 
mining a  rational  method  of  extracting  the  grease.  When  no 
special  circumstances  are  present  requiring  a  recovery  of  the 
grease,  or  when  the  sludge  does  not  possess  an  abnormally  high 
percentage  of  grease,  its  recovery  from  the  sludge  coming  from 
domestic  sewage  has  proved  irrational. 

The  recovery  of  grease  is  fairly  difficult,  as  it  is  so  intimately 
mixed  with  the  remaining  particles  of  sludge  that  the  specifically 
lighter  fatty  particles  do  not  rise  to  the  top,  or  do  so  with  great 
difficulty.  With  the  aid  of  the  previously  mentioned  grease  ex- 
tractors, separation  into  layers  of  sludge  rich  in  grease  and  poor 
in  grease  could  be  effected.  The  sludge  rich  in  fats  could  then 
be  worked  up  by  extraction  on  the  lines  of  the  method  described 
below.  In  practice  this  method  has  not  yet,  to  the  knowledge  of 
the  author,  been  applied. 

Further,  the  greasy  scum  obtained  from  sewage  from  slaughter- 
houses, hotels,  and  the  like  might  be  worked  up,  as  it  consists 
mainly  of  fats.  Whether  this  is  carried  out  in  practice  is  also 
unknown  to  the  author. 

According  to  Schiele,  the  sedimentation  plant  at  Bradford 
treats  a  sewage  from  wool  scouring  which  is  very  rich  in  grease, 
and  a  part  of  the  sludge  is  worked  up  for  grease  in  the  following 
manner:  After  addition  of  sulphuric  acid  the  sludge  is  heated 


106  SEWAGE   DISPOSAL 

to  100°  C.  and  expressed  in  hot  filter-presses.  The  greater  part  oi 
the  water  and  the  grease  is  thereby  removed.  The  residue  after 
expressing  still  contains  30  to  40  per  cent  water  and  25  per  cent 
grease.  From  the  filtrate  the  grease  separates  out  on  the  top, 
and  after  washing  and  deodorising  it  is  sold,  generally  to 
America.  In  the  Bradford  plant  the  total  sewage  must  be  treated 
with  sulphuric  acid  to  decompose  the  dissolved  soaps.  The 
proceeds  from  the  sale  of  grease  cover  about  half  the  cost  of  the 
sulphuric  acid.  The  grease  residues  remaining  over  are  burned 
with  one-eighth  the  amount  of  coal,  as  on  account  of  the  large 
percentage  of  grease  present  it  is  not  saleable  as  manure.  In  an 
experimental  plant  the  recovery  of  grease  from  the  press  residues 
was  tried.  The  residues  are  heated  in  retorts  from  which  the 
grease  distils  over.  The  residue  remaining  in  the  retort  should 
then  be  suitable  for  addition  to  artificial  manure,  since  it  contains 
some  phosphoric  acid  and  about  1-5  per  cent  nitrogen. 

The  town  of  Kassel  has  for  two  or  three  years  worked  a  grease- 
recovery  plant  with  a  machine  attached  to  their  sedimentation 
plant.  The  sludge  is  acidified  with  sulphuric  acid,  expressed  in 
filter-presses,  and  then  extracted  with  benzene.  The  reports 
sounded  very  favourable,  but  the  process  was  very  soon  dis- 
continued, due  to  the  firm  working  it  having  experienced  a  loss 
on  the  undertaking.  The  cause  of  the  non-success  lay,  firstly,  in 
the  high  cost  of  drying  the  sludge,  and  secondly,  in  the  yield  of 
grease  being  considerably  lower  than  was  anticipated. 

In  Frankfort,  extraction  of  wet  sludge  with  benzene  was  in- 
vestigated with  a  mechanical  arrangement  in  a  small  experi- 
mental plant.  A  practical  application  of  this  process  has  not  yet 
been  effected  on  the  large  scale. 

To  my  mind,  therefore,  no  solution  of  the  problem  of  grease 
recovery  from  sedimentation  sludge  need  be  expected.  It  is 
easy  to  be  attracted  by  the,  no  doubt,  considerable  value  of  the 
grease  present  in  these  residues.  Thus  the  grease  present  in 
Frankfort  sludge  obtained  in  one  year  has  a  worth  of 
about  £25,000.  If,  however,  in  order  to  recover  this  sum 
an  expenditure  of  £50,000  must  be  incurred,  the  transaction 
is  not  a  profitable  one.  According  to  Schiele,  an  English 
manufacturer  whose  attention  the  Royal  Commission  on  Sewage 
Disposal  drew  to  the  fact  that  in  his  effluents  there  was 
contained  so  much  valuable  material,  replied:  "It  is  worth  no 


PROFIT  FROM   SLUDGE  107 

more  to  me  than  a  piece  of  gold  at  the  bottom  of  the  sea.  It 
costs  me  too  much  to  get  it  up."  This  answer  can  be  adapted  to 
practically  all  attempts  at  the  recovery  of  grease  from  ordinary 
sedimentation  sludge.  In  addition  I  might  also  for  a  moment 
call  attention  to  something  to  which  up  to  the  present,  as  far  as 
I  know,  attention  has  not  been  directed.  To  a  judge  of  the 
circumstances  it  is  at  once  probable — and  the  plant  at  Kassel 
has  established  this  in  fact — that  benzene  extraction,  grease 
distillation  (for  the  recovery  of  pure  grease  from  crude  grease), 
and  other  operations  cannot  be  conducted  without  smells  ;  on 
the  contrary,  a  very  obnoxious  odour  is  generally  developed, 
which  is  noticeable  for  a  great  distance  around.  Now  municipal 
sedimentation  plants  are  by  no  means  all  far  away  from  the  town, 
so  that  there  is  a  danger  that,  with  a  diminution  in  the  rental 
value,  that  part  of  the  town  in  which  the  sedimentation  plant  is 
situated  may  depreciate  in  value.  However,  quite  apart  from 
aesthetic  and  hygienic  considerations,  which  must  be  urged 
against  a  continual  smell  owing  to  the  association  of  a  plant  and 
dwellings,  this  disadvantage  might  possibly  not  be  accompanied 
by  a  profit  from  the  sale  of  the  grease.  And  so  municipalities 
occupied  with  the  idea  of  recovering  grease  from  their  sewage 
can  only  be  pursued  with  the  cry  "  videant  consules." 

A  method  of  making  profit  frequently  adopted  of  late  years  is 
the  destruction  of  sludge  by  fire,  either  by  simple  burning  or  by 
gasification,  in  which  processes  the  heat  or  the  gases  obtained 
are  employed  in  the  production  of  other  forms  of  energy.  If  the 
sludge  cannot  be  burned  of  itself,  combustible  material  such  as 
turf,  coal,  borecole,  must  be  added.  Even  if  no  profit  results,  or 
the  cost  of  disposal  be  only  in  part  covered,  this  method  of  dis- 
posal or  of  realising  a  profit  from  these  residues  is  the  best,  as  it 
is  the  one  most  worthy  of  recommendation  from  the  hygienic 
point  of  view. 

The  town  of  Frankfort  now  disposes  of  its  sludge  in  the  following 
way  :  It  is  first  pumped  out  of  the  sedimentation  tanks  into 
large  reservoirs  which  are  situated  over  centrifuges  of  the  Schafer- 
ter-Mer  system.  In  these  reservoirs  a  portion  of  the  water  is 
separated  and  led  back  to  the  sedimentation  tanks.  The  sludge 
is  then  centrifuged.  It  is  then  mechanically  forwarded  to  a 
drying  drum,  in  which  the  centrifuged  material  with  about  70 
per  cent  water  is  further  dried  by  hot  gases  from  the  refuse 


108  SEWAGE   DISPOSAL 

destructor  plant.  The  sludge  coming  from  the  drum  still  contains 
about  25  per  cent  water,  and  is  now  burned  in  the  refuse  ovens. 
Addition  of  other  combustible  material  is  unnecessary,  as  the 
dried  sludge  burns  of  itself.  From  a  kilogram  of  sludge  about  a 
kilogram  of  steam  is  obtained.  Burning  of  the  sludge  is  therefore 
attached  to  the  refuse  destructor,  which  is  situated  near  the 
sedimentation  plant.  The  current  obtained  from  the  dynamos 
driven  by  the  burning  of  the  sludge  and  refuse  not  only  illuminates 
the  whole  plant  and  yields  power  for  the  plant,  but  there  is  also 
a  considerable  portion  conveyed  through  high-tension  cables  to  a 
pumping-station  in  the  Stadtwald,  where  by  means  of  the  current, 
electric  motor-pumps  are  worked  and  serve  to  raise  drinking- 
water.  Besides  this  there  is  a  considerable  amount  of  current 
delivered  to  the  town  supply. 

In  Bury  the  sludge  is  mixed  with  refuse  and  burned  (Schiele). 

In  Pforzheim  (Germany)  sludge  combustion  is  similarly 
provided  for  alongside  the  refuse  destructors. 

In  the  years  1902  and  1903  gasification  experiments  were 
carried  out  with  Frankfort  sludge  by  Bujard.  He  found,  as  the 
mean  of  two  experiments  with  gasification  lasting  four  hours, 
using  50  kilograms  of  dried  sludge,  the  following  volume  per- 
centages were  given  :— 

Yield  per  100  Ib.  sludge=320  cubic  feet  of  gas. 

Carbon  dioxide       .  .  ."....'        .         •.  16-1% 

Heavy  hydrocarbons  .  .          .       .  .          /  5 -8% 

Carbon  monoxide  .  ,  .          .       •  .. ',       ••  22-8% 

Methane     .   .          .  .  .          .        ,i.-        .  13-2% 

Hydrogen      .          .    '  .  .          .          .         -.  35'8% 

Nitrogen  (residue)  .  .  .          ...  6-3% 

Calorific  value  for  i  cubic  metre=362O  to  4072  W.E. 

Reichle  and  Dost  report  upon  gasification  experiments  with 
coal-pulp  sludge  :  Its  gasification  is  only  possible  with  a  certain 
amount  of  water  present,  which  must  not  be  over  58  per  cent ; 
the  gas  gave  on  the  average  in  volume  percentages  :— 

Methane o% 

Carbon  dioxide n-o% 

Nitrogen 62-6% 

Carbon  monoxide  ......  I4'2% 


PURIFICATION    OF   INDUSTRIAL   SEWAGE        109 

Oxygen 1-0% 

Hydrogen      ....  .      n-2% 

The  calorific  value  amounted  to  only  800  W.E.  The  gasifica- 
tion of  2-5  kilograms  of  the  sludge  with  about  51  per  cent  water 
yielded  about  i  horse-power  per  hour.  In  the  gasification  a 
grease-like  substance  distilled  over  ;  the  water  gas  in  the  dust-bag 
contained  2208  milligram  total  nitrogen  per  litre,  of  which 
1494  milligram  was  present  as  ammonia.  Reichle  and  Dost 
consider  that  the  introduction  of  gasification  with  the  sludge 
from  Degener's  coal-pulp  process  would  considerably  reduce  the 
high  cost  of  working  which  has  been  a  hindrance  up  to  the 
present,  and  conduce  to  the  more  general  introduction  of  this 
otherwise  very  advantageous  process. 

In  the  town  of  Kopenick,  near  Berlin,  coal-pulp  sludge  is 
gasified  on  a  large  scale.  The  power  gas  obtained  is  converted 
into  electrical  energy. 

B.     Purification   of  Industrial   Sewage. 
I.    GENERAL. 

Most  towns  take  industrial  effluents  into  their  drainage  system 
in  return  for  a  fee  ;  they  then  demand  that  the  sewage  never 
contains  substances  harmful  to  the  drains  (acids,  alkalies,  com- 
bustible material,  etc.),  and  that  the  purification  of  the  whole 
sewage  is  not  rendered  much  more  difficult  as  a  consequence  of 
the  introduction.  Consequently,  there  are  already  large  manu- 
facturing towns  whose  sewage  contains  quite  considerable 
amounts  of  industrial  sewage  admixed.  For  purifying  such 
municipal  sewage  chemical  precipitation  is  to  be  recommended 
in  the  sedimentation  plants.  With  contact  beds  and  percolating 
filters  the  plant  must  be  larger  in  its  dimensions  than  would  be 
necessary  for  the  corresponding  amounts  of  domestic  sewage. 
The  reception  of  industrial  sewage  makes  the  process  of  sewage 
purification  more  expensive  for  municipalities.  Nevertheless, 
the  endeavour  to  receive  industrial  effluents  into  the  ordinary 
sewerage  system  is  to  be  welcomed  and  recommended.  Other- 
wise separate  plants  in  the  various  manufactories  must  result  to 
a  great  degree.  Now  larger  plants,  for  the  reasons  which  have 
already  been  frequently  mentioned  in  other  chapters,  are  worked 


110  SEWAGE   DISPOSAL 

more  rationally  and  with  greater  security  than  smaller  plants. 
Again,  the  erection  of  separate  sedimentation  plants  is  contrary 
to  all  the  fundamental  principles  of  drainage  systems,  according 
to  which  all  refuse  should  as  far  as  possible  be  conveyed  out  of  the 
town.  With  manufacturing  plants,  however,  the  residues  must 
be  allowed  to  accumulate  on  the  works'  premises. 

Although  it  seems  desirable  to  convey  industrial  sewage 
through  the  ordinary  sewers,  there  are  still  very  many  cases  in 
which  purification  of  industrial  sewage  itself  is  necessary.  Where 
towns  refuse  to  receive  the  sewage  or  demand  a  previous  slight 
superficial  purification,  and  where  there  is  no  sewage  system  as 
in  works  and  in  isolated  places,  the  industrial  effluents  must 
themselves  be  purified  if  the  stream  conducting  it  away  is  not  to 
be  harmed  by  the  incoming  sewage.  Therefore  the  purification 
of  industrial  sewage  is  a  question  becoming  ever  increasingly 
important. 

The  sewage  produced  in  works  can  be  divided  into  three 
groups  : — 

(1)  Closet,  cooking,  washing,  and  bathing  water. 

(2)  Condenser,  cooling,  and  washing  water. 

(3)  The  particular  works  sewage. 

The  first  group  comprise  effluents  which  are  domestic  in 
character,  whose  purification  has  been  described  in  the  previous 
chapter. 

The  kinds  of  sewage  named  in  section  2  are  generally  very  pure. 
It  is  always  advisable  to  keep  them  separate  from  the  particular 
forms  of  sewage  of  the  third  group,  as  if  this  is  not  done  the 
sewage  is  simply  diluted  and  the  difficulties  of  purification  are 
considerably  increased.  This  is  to  be  recommended,  as  the  water 
from  the  second  class  often  very  considerably  preponderates  over 
that  of  the  third.  Cleansing  and  condenser  water  is  frequently  so 
pure  that  it  can  be  drained  away  without  any  purification  or 
after  treatment  in  a  sedimentation  tank. 

To  give  a  general  composition  for  particular  works  effluents  is 
naturally  impossible,  as  this  depends  wholly  on  the  nature  of  the 
work  carried  out.  It  is  therefore  also  impossible  to  set  forth 
general  rules  for  the  purification  of  industrial  sewage.  Only  this 
much  can  be  said,  that  the  general  principles  of  purification  are 
the  same  as  in  the  case  of  domestic  sewage,  and  therefore  consist 
of  either  mechanical  purification  by  sedimentation  tanks,  or 


'  PURIFICATION   OF   INDUSTRIAL   SEWAGE        111 

biological  purification  by  broad  irrigation,  contact  beds,  or 
percolating  filters.  In  the  sedimentation  process  it  is  always 
advisable  to  make  use  of  chemical  precipitation,  with  the  addition 
of  chemicals  which  have  been  proved  to  be  suitable  by  experi- 
ment for  the  particular  kind  of  sewage. 

It  is  to  be  recommended  much  more  with  industrial  effluents 
than  with  household  sewage  that  tests  be  made,  on  the  basis  of 
a  chemical  investigation  of  the  sewage,  to  determine  the  most 
suitable  method  of  purification. 

Frequently,  of  course,  partial  purification  is  to  be  attained  by 
combination  of  different  kinds  of  effluents.  Thus,  acid  and  alkali 
discharges  partially  neutralise  one  another.  Effluents  con- 
taining lime  precipitate  heavy  metals  or  alumina  and  the  like. 
Such  a  combination  of  the  various  effluents  is  often  sufficient  to 
effect  sufficient  purification  after  sedimentation. 

An  arrangement  which  can  be  recommended  for  works  clari- 
fying plants  is  the  keeping  of  a  reservoir.  It  is  now  used  in  very 
many  works  in  which  at  one  time  highly  polluted  and  large 
amounts  of  sewage  are  produced,  and  at  other  times  little  and 
only  slightly  polluted  sewage  is  formed.  For  if  large  amounts  of 
strongly  polluted  sewage  are  suddenly  conveyed  to  a  stream,  it 
means  much  greater  harm  is  being  done  to  the  river  than  if  the 
whole  sewage  of  24  hours  was  slowly  and  uniformly  discharged 
into  the  river.  For  this  purpose  tanks  must  be  laid  down  capable 
of  storing  the  effluent  resulting  from  a  day's  working.  Now  and 
then,  when  the  river  is  sufficiently  high  and  the  sewage  does  not 
seem  too  filthy,  further  purification  than  is  assured  in  these 
reservoirs  is  quite  unnecessary. 

Lately,  also,  industrial  effluents  have  been  used  to  lay  the  dust 
on  the  roads. 

According  to  Weldert,  for  this  purpose,  under  certain  circum- 
stances, there  come  into  consideration  effluents  from  ammonia 
works,  potash  works,  cellulose  works,  sugar  refineries,  coke 
plants,  spinning  mills,  wool  factories,  fulling  mills,  and  ammonia- 
soda  works.  Experiments  of  Weldert  with  ammonia  effluents 
yielded  favourable  results.  The  problem  of  dust-laying  will  be 
more  closely  studied  under  the  various  particular  classes  of  sewage. 

For  the  purification  of  works  sewage  the  filter  is  frequently 
used.  Under  the  term  "  filter  "  no  biological  filters  are  under- 
stood, but  apparatus,  constructed,  of  course,  of  similar  materials 


112  SEWAGE   DISPOSAL 

to  them,  but  which,  however,  are  worked  continuously.  Their 
action  therefore  is  the  purely  mechanical  one  of  retaining  the 
suspended  matter.  They  are  generally  prepared  of  cheap  un- 
sieved  material,  clinkers  from  boiler-fires  predominating.  This 
filter  is  used  both  for  the  subsequent  purification  of  clarified 
works  sewage  and  also  for  the  removal  of  water  from  sludge 
(Magma  Filter) .  For  the  treatment  of  percolating  filter  discharge 
such  filters  are  also  used. 

II.     THE   PURIFICATION    OF    INDUSTRIAL   SEWAGE 
IN    PARTICULAR. 

With  Fowler  and  Ardern  we  can  classify  industrial  effluents, 
according  to  the  substances  through  which  they  act  harmfully, 
thus  :— 

(1)  Effluents  with  large  quantities  of  suspended  matter. 

(2)  Effluents  with  substances  that  may  decompose. 

(3)  Coloured  effluents. 

(4)  Effluents  containing  poisons. 

(5)  Effluents  containing  oils,  tars,  fats,  soaps,  etc. 

Many  effluents  may  naturally  come  under  several  of  the  head- 
ings mentioned. 

Effluents  of  the  first  kind  can  generally  be  sufficiently  purified 
by  settling  devices,  sieves,  rakes,  filters,  etc.  Effluents  from 
coal-washing  and  cloth  factories,  etc.,  might  be  named  here. 

Effluents  of  the  second  kind  are  very  disagreeable.  They  are 
purified  by  chemical  precipitation  with  subsequent  sedimenta- 
tion, or  by  the  land  treatment,  or  by  means  of  contact  beds  or 
percolating  filters,  as  was  set  forth  in  the  previous  section.  The 
chief  and  most  important  effluents  belong  to  this  class,  for 
example,  those  from  tanneries,  cellulose  works,  breweries,  sugar 
refineries,  etc. 

The  purification  of  coloured  effluents  is  still  an  unsolved 
problem.  No  method  is  yet  known  of  decolorising  coloured 
substances -in  a  satisfactory  and  continuous  manner.  In  general 
decolorisation  is  more  difficult,  the  faster  the  colours.  Chemical 
precipitation  and  various  biological  methods  are  employed. 
With  contact  beds  and  percolating  filters  the  colouring  matter  is 
absorbed  by  the  beds  for  a  time,  but  after  a  certain  period  the 
colour  passes  through  unchanged. 


PURIFICATION   OF   INDUSTRIAL   SEWAGE 

Purification  of  sewage  containing  poisons  must  naturally 
depend  on  the  chemical  nature  of  the  poison.  Acids  are  generally 
neutralised  with  lime,  and  alkalis  with  sulphuric  acid.  Heavy 
metals  are  precipitated  by  lime,  etc.  Cyanides  can  be  separated 
as  Prussian  blue  with  sulphate  of  iron  and  caustic  soda.  Under 
this  heading  is  comprised  sewage  from  metal  works,  gas  works, 
tanneries,  sulphite  cellulose  works,  etc. 

Sewage  containing  oils,  fats,  and  soaps  are  finally  purified  by 
the  separation  of  the  fat  particles,  in  the  case  of  soaps  after  the 
addition  of  sulphuric  acid.  Under  this  heading  are  the  effluents 
from  margarine  works,  wool-scouring  works,  slaughter-houses, 
etc.,  which  may  also  all  be  reckoned  under  section  2. 

According  to  this  general  point  of  view  an  industrial  effluent 
may  be  classified  and  the  manner  in  which  the  purification 
process  has  to  be  carried  out  may  be  given.  The  extraordinary 
variety  of  particular  effluents  in  the  four  groups  makes  a  closer 
examination  of  the  particular  kinds  of  sewage  seem  worthy  of 
attention.  I  shall  endeavour  to  mention  all  the  classes  of  sewage 
coming  at  any  time  into  consideration. 

(i)    Sewage  from  Cloth  Factories  or  Factories  whose  Effltients 
contain  Fibrous  Material. 

Reichle  and  Zahn  describe  a  drum  filter  by  A.  and  A.  Lehmann 
that  is  very  suitable  for  recovering  fibre  of  any  kind  from  sewage. 
The  apparatus  consists  of  a  movable  drum  which  is  covered  with 
wire  netting  i  millimetre  mesh.  The  sewage  streams  through 
the  drum  and  leaves  the  fibre  behind.  From  the  works  in  ques- 
tion 22  tons  of  wool  were  obtained  in  nine  months. 


(2)  Sewage  from  Cardboard  Factories. 

According  to  the  laboratory  experiments  of  Sjollema,  the 
addition  of  monocalcium  phosphate  (superphosphate)  is  most 
suitable  for  the  purification  of  this  sewage,  as  it  forms  tricalcium 
phosphate  with  the  free  lime  present  in  solution.  This  is  pre- 
cipitated out  and  settles  down  along  with  the  suspended  matter, 
together  with,  also,  a  portion  of  the  dissolved  substances.  The 
precipitate  after  drying  can  be  used  as  manure. 


114  SEWAGE   DISPOSAL 

(3)  Sewage  from  Straw-board  Works. 

These  works  produce  very  large  amounts  of  sewage,  which 
contain  many  fine  particles  of  straw  mixed  with  lime. 

The  sewage  can  be  purified  by  sedimentation  (capacity  of  the 
tanks  being  one  hour's  supply)  and  by  filtration  through  me- 
chanical filters  without  the  addition  of  a  precipitant  (rate  of 
filtration  equal  to  95  cb.m.  through  i  sq.m.  of  filter  every  24 
hours).  The  filtered  sewage  can  then  be  used  again  in  the  works. 
According  to  Kimberley,  the  sewage  so  purified  can  be  drained 
into  the  river  without  harm  if  the  stream  contains  twice  the 
amount  of  water  present  in  the  sewage.  Sjollema  recommends 
his  above-mentioned  precipitation  method  with  superphosphate 
for  this  sewage. 

(4)  Effluents  from  Mines  (Coal-washing) . 

Effluents  from  waterworks  in  mines  consist  of  waters  from 
washing  coal  and  from  quenching  coke.  It  is  not  advisable  to 
purify  these  effluents  along  with  domestic  sewage,  for  then  the 
sedimentation  tanks  have  to  be  built  abnormally  large.  In  the 
quenching  of  coke  the  water  is  used  over  and  over  again  ;  from 
time  to  time,  however,  it  must  be  withdrawn  from  circulation 
and  purified.  This  is  generally  effected  in  settling  tanks.  The 
Imhoff-Lagemann  patent  is  especially  suitable  for  this  purpose. 
The  bottom  of  this  tank  is  drained.  The  drains  terminate  outside 
the  settling  tank  and  are  closed  during  the  settling  process. 
They  are  opened  only  to  dry  the  sludge. 

Sometimes  before  its  entry  into  the  river  the  sewage  is  allowed 
to  flow  through  a  filter  of  boiler-clinkers.  The  coal  sludge  ob- 
tained is  either  burned  or  worked  up  as  coke. 

According  to  the  experiments  at  the  Halle  Agricultural- 
Chemical  Experimental  Station,  the  resinous  water  from  borecole 
coke  works  is  especially  suitable  as  manure,  since  it  may  develop 
a  considerable  nitrifying  action  without  fear  of  any  harm  being 
done  to  the  plants  by  manuring  the  roots.  It  is  most  strongly 
recommended  as  a  manure  for  meadow  or  pasture  land. 

(5)    Sewage  from  works  Granulating  Slag. 

Many  works,  e.g.,  smelting  works,  have  plants  for  granulating 
slag.  The  fluid  slag  is  allowed  to  flow  into  water,  by  which  means 


PURIFICATION   OF   INDUSTRIAL   SEWAGE        115 

it  is  broken  into  small  pieces.  The  effluents  resulting  from  this 
are  hot  and  contain  large  amounts  of  fine  slag,  of  which  a  part 
sinks  and  another  part  floats  on  the  surface. 

The  firm  "  Stadtereinigung  und  Ingenierbau-A.-G.,  Berlin- 
Wiesbaden  "  have  constructed  devices  for  the  purification  of 
such  effluents  which  should  work  quite  satisfactorily.  The  idea 
of  these  plants  is  that  the  sewage  is  led  with  fairly  slow  velocity 
through  a  sedimentation  tank,  by  which  means  the  heavy 
particles  sink  to  the  bottom.  The  floating  material  is  removed 
by  the  aid  of  several  channels  which  are  placed  obliquely  to  the 
direction  of  flow,  and  are  provided  with  various  devices  cor- 
responding to  the  purpose  for  which  they  are  constructed.  The 
floating  slag  skimmed  off  is  led  into  a  second  tank  which  is  at 
rest,  and  in  this  the  floating  substances  are  stored  up  until  the 
layer  has  reached  a  certain  strength.  Thereupon  the  water 
underneath  is  drained  away,  so  that  the  scum  sinks  to  the  bottom. 
The  slag  from  the  two  tanks  is  then  bagged. 

(6)   Sewage  from  Paper  Mills  and  Cellulose  Works. 

In  the  manufacture  of'  paper,  rags,  hemp,  jute,  esparto  grass, 
straw,  and  wood  are  all  used. 

The  main  effluent  from  all  these  raw  materials  is  the  alkaline 
water  obtained  by  boiling  them.  To  this  must  be  added  the  water 
from  washing  and  cleansing  the  raw  materials  after  they  have 
been  digested,  the  discharge  from  the  Hollanders,  the  water 
containing  both  acid  and  chlorine  from  the  bleaching  process, 
and  finally  the  discharges  from  the  paper  machines  and  dyeing 
process. 

Separate  treatment  of  the  different  kinds  of  effluent  is  advis- 
able. The  sewage  coming  from  the  paper  machines  allows  of  a 
recovery  of  the  fibrous  material  in  specially  erected  settling 
tanks,  and  the  effluent  therefrom  may  be  used  again.  The  above 
sewage  may  be  purified,  however,  to  the  requisite  degree  by 
chemical  precipitation  and  sedimentation  or  by  means  of  sand 
filters. 

The  effluents  from  wood-pulp  or  cellulose  works  are  of  great 
importance.  Cellulose  in  Germany  is  entirely  prepared  by  the 
sulphite  process.  Fir  and  pine  is  treated  in  so-called  digesters 
or  boilers  at  high  temperatures  and  under  pressure  with  calcium 


116  SEWAGE    DISPOSAL 

bisulphite.  The  soluble  material  is  thereby  removed  and  the 
wood  fibre  isolated.  The  fibrous  residue  is  then  expressed  and 
washed  free  from  the  strong  liquors.  There  thus  accrue  to  the 
sewage  :  boiler  liquors  and  washing  liquors,  water  from  the  sieves, 
presses,  and  from  the  machines  for  removing  water  from  the 
cellulose,  in  addition  to  condenser  water.  The  boiler  liquors  are 
the  worst,  for  they  contain  about  100  grammes  of  organic  matter 
per  litre,  and  consequently,  if  conveyed  to  the  river  without 
further  treatment,  cause  grave  inconvenience  owing  to  putre- 
faction, and  especially  to  the  formation  of  fungi  (Sphaerotilus) . 

In  most  works  the  sewage  undergoes  a  superficial  purification. 
The  suspended  matter  is  filtered  off  after  a  partial  recovery  of 
the  sulphur  acids,  and  the  liquors  are  cooled  down  and  neutralised 
with  lime.  The  sewage  is  subsequently  treated  in  sedimentation 
tanks.  Dissolved  material  is,  however,  scarcely  influenced  by 
this  process,  and  they  are  the  substances  that  exert  a  harmful 
influence  on  the  river  carrying  the  sewage  away.  The  purifica- 
tion of  the  liquors  by  the  biological  process  is  impossible,  even  after 
great  dilution  of  the  sewage,  firstly  on  account  of  the  difficulty 
of  decomposing  the  liquors,  and  secondly  on  account  of  the 
harmful  action  on  the  micro-organisms  of  the  sulphurous  acids 
present  in  the  lye. 

Possibilities  of  making  a  profit  from  such  sewage  have  been 
investigated,  and  the  very  numerous  proposals  made  with  this 
object  in  view  have  only  partly  led  to  practical  results.  Evapora- 
tion and  combustion  of  the  product  is  very  costly,  and  the  works' 
profit  comes  into  the  question.  In  rare  cases  only  is  the  sewage 
allowed  to  trickle  away,  and  this  depends  on  the  local  circum- 
stances. 

Researches  on  the  recovery  of  sulphur,  on  the  employment 
of  the  organic  substances  in  the  liquors  as  combustible  material, 
whether  directly  or  after  making  briquettes  of  it  with  coal,  coke, 
or  furnace  dust,  have  not  yet  yielded  any  practical  results. 
Further,  it  is  proposed,  after  the  removal  of  harmful  material, 
especially  the  sulphur  acids,  to  work  up  the  liquors  as  feeding- 
stuffs  ;  these  proposals,  also,  have  not  been  put  into  practice. 
On  the  contrary,  the  liquors  have  been  used,  after  certain  sub- 
stances have  been  added,  as  adhesives,  and  most  recently  have 
been  used  to  lay  the  dust  on  the  streets.  Their  value  as  manure 
to  be  added  to  "  Thomasmehl,"  and  their  application  in  tanneries, 


PURIFICATION   OF   INDUSTRIAL  SEWAGE        117 

are  still  undecided  questions.  Fermentation  of  the  sugar  pro- 
ducts found  in  the  residues  and  the  recovery  of  alcohol  is  already 
carried  out  in  practice  in  Sweden,  but  in  Germany  the  pursuit 
of  this  process  is  not  profitable  owing  to  the  big  duty  which  is 
paid  on  alcohol  since  the  recent  legislation  concerning  duty  on 
brandy.  The  recovery  of  colouring  matter  from  the  boiler  liquors 
is  already  a  successful  process,  but  the  problem  needs  further 
investigation  (Pritzkow) . 

Besides  the  "  sulphite  "  process,  there  is  the  "  soda  "  process 
for  the  preparation  of  cellulose,  in  which  the  wood  is  digested 
with  caustic  soda  instead  of  calcium  sulphite.  The  method  is  by 
no  means  as  important  as  the  sulphite  process.  The  caustic  soda 
liquors  are  the  worst  effluents  in  this  case,  and  are  to  be  as  care- 
fully treated  as  the  sulphite  strong  liquors. 

Logau  evaporates  the  residues  and  ignites  them  ;  the  heat 
obtained  by  the  ignition  is  used  in  evaporating  further  quantities 
of  the  liquors.  Fire  for  combusting  the  material  only  needs  to  be 
used  at  the  commencement  of  the  operation.  Soda  is  recovered 
from  the  ashes.  Rimman  saturates  the  liquors  with  carbon 
dioxide  after  they  have  been  raised  to  a  certain  specific  gravity 
by  the  addition  of  soluble  salts.  A  part  of  the  organic  matter 
present  is  thus  precipitated. 

(7)  Sewage  from  Breweries. 

The  major  portion  of  brewery  sewage  is  cleansing  and  washing 
water.  It  is  consequently  only  slightly  polluted.  On  the  other 
hand,  the  effluents  of  the  process  itself  are  greatly  polluted, 
especially  those  from  the  malting,  from  the  drying  of  the  hops 
and  grain,  and  from  the  yeast.  This  sewage  has  a  strong 
tendency  towards  putrefaction  on  account  of  the  large  amount 
of  organic  matter  that  it  contains.  It  has  a  tendency  also  to 
form  lactic  acid. 

Partial  purification  consists  of  chemical  precipitation  followed 
by  sedimentation. 

This  kind  of  purification  is,  however,  generally  insufficient. 

Where  more  thorough  purification  is  impossible,  the  sewage 
should  be  immediately  conveyed  to  the  drains. 

Brewery  sewage  is  best  purified  by  land  irrigation. 

After  the  addition  of  lime  (neutralisation  of  the  lactic  acid) 


118  SEWAGE   DISPOSAL 

these  effluents  can  be  purified  on  contact  beds,  but  best  of  all  in 
percolating  filters. 

(8)  Tannery  Sewage. 

In  tanneries  there  are  principally  three  classes  of  effluent, 
from  the  liming  process,  the  dye  liquors,  and  tanning  liquors. 

The  lime  effluents,  which  result  from  the  unhairing  or  depila- 
tion  of  the  hide,  contain  lime  principally,  sodium  sulphide,  and  a 
large  amount  of  decomposable  organic  substances  (pieces  of  hide, 
hair).  Under  certain  circumstances,  if  foreign  hides  are  being 
worked  up,  napthalene  may  be  present  as  a  preservative  for  the 
skins. 

Tanning  liquor  contains  either  tannic  acid  or  chromium  salts. 
The  tanning  effluents  therefore  contain  these  substances.  Fre- 
quently, also,  other  chemical  compounds  like  sodium  thiosul- 
phate,  arsenic  salts,  etc.,  are  present. 

The  dyeing  liquors  are  used  to  dye  the  leather  ;  the  sewage 
resulting  from  this  part  of  the  industry  has  the  same  colour  as 
the  dyeing  liquors. 

All  tannery  effluents  are  generally  putrefactive  to  an  unusually 
large  extent.  They  therefore  have  a  very  harmful  action  on  the 
stream  conveying  them  away  if  they  are  led  into  it  directly  or 
with  insufficient  purification. 

They  are  therefore  best  run  into  the  drains  after  preliminary 
purification  in  settling  tanks.  According  to  Schmidtmann, 
Thumm,  and  Reichle,  they  will  even  then  frequently  give  trouble, 
when,  for  example,  tan  sewage  containing  sodium  sulphide  comes 
into  contact  with  acid  effluents,  like  those  from  breweries.  The 
resulting  evolution  of  sulphuretted  hydrogen  will  be  a  great 
source  of  annoyance  in  the  streets. 

If  it  is  not  possible  to  run  the  sewage  into  the  sewers,  a  large 
reservoir  is  to  be  recommended  for  a  works. 

A  partial  purification  can  be  attained  occasionally  by  com- 
bining the  various  kinds  of  effluent.  The  lime  from  the  liming 
process  precipitates  chromium  salts,  and  then  the  sewage  is 
clarified  in  settling  tanks.  In  certain  cases,  therefore,  chemical 
precipitation  can  be  dispensed  with.  It  is  better,  however,  to  add 
chemicals  in  calculated  quantities. 

When  more  thorough  purification  is  necessary  it  is  best  to  use 
broad  irrigation,  preceded  by  treatment  in  septic  tanks.  If  the 


PURIFICATION   OF  INDUSTRIAL  SEWAGE        119 

artificial  biological  process  is  employed,  double -contact  beds 
seem  to  work  better  than  percolating  filters.  Arsenic  and  other 
poisonous  substances  must  be  removed  before  any  biological 
purification  is  taken  in  hand. 

(9)  Sewage  from  Dairies  and  Margarine  Works. 

The  sewage  from  such  places  contains  particles  of  milk 
collected  together.  One  would  therefore  expect  albumens, 
carbohydrates,  fat,  lactic  acid,  etc.,  in  such  effluents,  which  are 
therefore  highly  putrefactive. 

Kimberley,  acting  for  a  Commission  in  the  State  of  Ohio, 
U.S.A.,  undertook  a  detailed  investigation  of  the  sewage  from 
dairies.  If  the  amount  of  water  in  the  river  receiving  the  sewage 
be  thirty  times  as  great  as  the  sewage  itself,  then,  according  to 
this  author,  dairy  effluents  can  be  discharged  into  the  river  after 
treatment  in  settling  tanks.  These  tanks  should  be  twice  as 
large  as  a  day's  effluent  requires. 

In  other  cases,  dairy  effluents  may  be  purified  by  intermittent 
sand  filtration  until  they  are  incapable  of  putrefaction  (22,000 
gallons  per  acre  of  filter  surface). 

In  Germany  they  are  frequently  purified  by  ordinary  land 
irrigation.  They  are  generally  previously  clarified  in  masonry 
tanks.  To  prevent  nuisances  due  to  bad  odours  disinfectants 
(chloride  of  lime)  are  added  to  the  sewage  in  the  tanks.  According 
to  Guth  a  good  soil  cannot  take  up  more  than  6  gallons  per  square 
yard.  Grass,  clover,  and  trees  thrive  very  well  on  the  fields 
irrigated.  In  the  opinion  of  Dunbar,  an  effluent  from  a  dairy,  if 
not  too  concentrated,  can  be  purified  by  the  biological  processes, 
and  most  successfully  with  percolating  filters  continuously 
employed.  For  the  biological  process  the  sewage  must  be  pre- 
viously purified  by  chemical  precipitation,  to  neutralise  the  lactic 
acid,  as  otherwise  purification  would  be  insufficient.  According 
to  Guth,  not  more  than  a  cubic  metre  of  sewage  should  be  applied 
to  a  square  metre  of  surface,  that  is,  0-5  cubic  metre  of  filter 
material. 

Harm  precipitates  dairy  effluents  with  acid  silicates  (the  waste 
from  the  manufacture  of  alum)  and  with  lime.  He  asserts  that 
he  has  obtained  good  results  from  lengthy  investigations.  Informa- 
tion is  lacking  as  to  the  cost  and  the  resulting  sludge. 


120  SEWAGE   DISPOSAL 

Partial  purification  can  be  attained  by  precipitation  with 
sulphate  of  iron  and  lime,  followed  by  sedimentation. 

(10)  Sewage  from  Slaughter-houses,  Knackers'  Yards,  and 
Glue  Works. 

Slaughter-house  sewage  is  generally  very  concentrated,  is 
readily  decomposed,  and  has  an  especially  harmful  action  on  the 
stream  receiving  it.  It  contains  blood,  fat,  flesh,  manure,  and 
slaughter-house  refuse  of  every  kind. 

It  may  be  partially  purified  by  treatment  with  iron  or  alu- 
minium sulphates,  followed  by  sedimentation. 

For  mechanical  purification  automatically  working  clarifying 
boilers  by  Mertens  of  Berlin  have  been  employed  (Swinemunde, 
Paderborn-i.-W.). 

In  Kiel,  during  1905,  an  experimental  plant  was  erected  for 
the  purification  of  slaughter-house  effluents  by  means  of  the 
biological  process.  Meanwhile,  many  towns  have  employed  it 
for  the  work  with  success.  Preliminary  purification  in  septic 
tanks  should  be  very  suitable  with  such  sewage. 

Thiesing  studied  the  sewage  coming  from  the  knacker's  yard 
and  also  its  disposal.  It  comprises  the  water  used  in  cleaning 
the  places  in  which  the  horses  are  killed,  the  glue  liquors,  the 
waste  liquors  from  steaming  the  carcases,  the  glue  condenser 
water,  and  mixtures  of  these  kinds  of  sewage.  They  are  all  very 
concentrated  and  readily  decomposable.  Up  to  the  present, 
according  to  Thiesing,  the  treatment  employed  with  such  effluents 
has  always  been  insufficient.  It  is  necessary  to  observe  that 
rain-water  does  not  pass  through  the  purification  plant.  On  the 
other  hand,  domestic  sewage  may  be  treated  along  with  it. 
Broad  irrigation  and  the  biological  process  should  be  very 
suitable  for  the  purification  of  such  sewage.  With  such  treat- 
ment preliminary  purification  in  septic  tanks  and  grease  separa- 
tors is  to  be  recommended. 

(n)  Sewage  from  Sugar  Refineries. 

The  sewage  from  sugar  refineries,  besides  condenser  water, 
which  is  harmless,  consists  of  water  from  the  washing  of  the  beet, 
from  the  diffusers,  and  the  filter-presses. 


PURIFICATION   OF  INDUSTRIAL  SEWAGE        121 

The  different  kinds  of  sewage  must  be  treated  separately. 
The  water  used  in  washing  the  beet  is  purified  in  sedimentation 
tanks  and  then  used  again.  Markwart  would  like  to  run  the 
water  from  the  diffusers  and  from  the  presses  into  the  diffusers 
again  without  further  treatment.  It  is  then  necessary  to  prevent 
fermentation  from  being  set  up. 

According  to  Herzfeld,  the  following  important  preliminary 
must  be  observed  before  using  the  effluents  again  in  the  process, 
viz.  the  particles  of  pulp  must  be  removed  by  careful  sedi- 
mentation. 

Hoyermann  and  Wellensiek  recommend  for  the  purification 
of  sewage  from  sugar  factories  one  of  their  own  preparations, 
which  consists  of  humic  acids  which  are  hydrolysed  with  alkalies. 
In  the  process  of  hydrolysis  the  solubility  of  the  humins  is  quite 
considerably  increased.  The  sewage  to  be  purified  is  treated 
with  humin  suspended  in  water,  and  then  lime  is  added  till  the 
whole  is  weakly  alkaline.  As  a  result  a  flocculent  precipitate 
separates  out,  and  the  water  becomes  quite  bright  and  clear ;  the 
precipitate  settles  quickly.  According  to  Schone,  the  nitrogen 
content  of  the  effluent  from  the  slicers  should  be  lowered  by 
about  69  per  cent  after  treatment  by  the  Hoyermann-Wellensiek 
process.  The  sewage  should  then  also  be  incapable  of  putrefying. 
According  to  the  report  of  the  Proceedings  of  the  Technical 
Association  of  Sugar  Manufacturers  at  their  conference  in  Magde- 
burg, on  the  2ist  March,  1911,  the  following  managers,  Gehrke 
(Alleringersleben),  Thiel,  Griinanger  (Niederdodeleben),  and  Dr. 
Dietrich  (Gehrden),  who  have  all  employed  the  process  for  the 
purification  of  their  effluents,  expressed  themselves  very  favour- 
ably with  regard  to  it. 

A  German  ministerial  decree  of  the  4th  of  July,  1910,  by  the 
President  of  the  Government,  explains  that  the  question  of  using 
the  effluents  from  the  diffusion  process  and  from  the  slicers  has 
proved  to  be  practicable  in  technical  work,  so  that,  in  those  cases 
in  which  nuisances  arise  from  introducing  these  effluents  into 
the  stream  unpurified,  the  police  authorities  might  be  justified 
in  forbidding  their  introduction. 

The  water  from  the  presses  is  often  purified  thus :  It  is  first 
heated  in  fermentation  tanks,  then  neutralised,  after  which  it 
is  drained  on  fields,  being  subsequently  collected  and  used 
again. 


SEWAGE   DISPOSAL 

De  Plato  treats  the  filtered  water  with  milk  of  lime  (15°  Be) 
until  completely  precipitated,  and  then,  after  sedimentation, 
with  a  five  per  cent  solution  of  calcium  hypochlorite.  The  water 
is  next  decanted  and  led  through  five  cylinders  filled  with  lumps 
of  coke.  Analysis  showed  that  about  50  per  cent  of  the  organic 
matter  is  thereby  removed  ;  the  effluent  should  then  be  harmless 
to  the  fish  in  the  river. 


(12)  Sewage  from  Starch  Factories. 

Starch  factories  may  use  corn,  maize,  rice,  or  potatoes.  The 
sewage  varies  with  the  kind  of  raw  material.  Starch  factories 
employing  rice  and  maize  have  effluents  containing  some  free 
alkali,  and  now  and  then  some  sulphurous  acids. 

Generally  the  sewage  from  starch  factories  is  similar  to  that 
from  sugar  factories.  It  contains  a  large  amount  of  organic 
matter,  whilst  fermentation  and  putrefaction  readily  occur. 
In  Germany  potatoes  are  mainly  used  as  raw  material  in  the 
manufacture  of  starch.  From  a  hundredweight  of  potatoes 
there  is  about  50  to  70  gallons  of  sewage,  which  consists  of 
waters  from  washing  the  potatoes,  the  by-products  and  the 
starch,  together  with  refuse  from  the  pulp-presses. 

The  sewage  is  clarified  in  settling  tanks.  The  effluent,  which 
is  acid  in  reaction,  is  frequently  drained  away  after  this  simple 
clarification.  The  sludge  is  from  time  to  time  worked  up  for 
starch. 

With  the  Hoyermann-Wellensiek  process  mentioned  under 
sugar-factory  sewage,  75  per  cent  of  the  organic  matter  from  the 
starch  sewage  is  separated. 

C.  Zahn  made  a  detailed  investigation  of  the  possibility  of 
purifying  sewage  from  starch  factories  by  means  of  the  biological 
process.  The  use  of  septic  tanks  instead  of  sedimentation 
tanks  is  not  to  be  recommended.  Purification  was  better  the 
finer  the  material  composing  the  beds,  so  that  with  starch-factory 
effluents  contact  beds  are  superior  to  percolating  filters.  It  is 
advantageous  here,  also,  to  neutralise  the  sewage  before  passing 
it  on  to  the  beds.  Zahn  effected  this  neutralisation  by  mixing 
acid  sewage  with  some  alkaline  effluents,  or  else  by  means  of  lime- 
stone laid  down  in  the  beds.  For  the  preparation  of  the  beds  the 
use  of  materials  free  from  iron  is  to  be  recommended.  With  a 


PURIFICATION   OF   INDUSTRIAL   SEWAGE 

diminution  of  80  per  cent  in  the  oxidisability  of  the  s.ewage  there 
was  nevertheless  subsequent  decomposition,  so  that  Zahn  urges 
the  adoption,  in  the  case  of  industrial  effluents,  of  the  views  held 
in  regard  to  domestic  sewage. 

(13)  Sewage  from  Distilleries  and  Yeast  Works. 

This  sewage  contains  a  large  amount  of  organic  matter  both 
dissolved  and  in  suspension.  It  is  therefore  strongly  putre- 
factive. The  effluents  from  the  yeast-presses  and  from  the  dis- 
tillation of  the  wort  are  the  chief  concern  in  these  processes. 

They  are  best  disposed  of  as  food  for  cattle.  They  may  be 
roughly  purified  by  chemical  precipitation  (alum  and  lime)  and 
by  sedimentation  in  tanks. 

They  may  be  thoroughly  purified  by  land  treatment,  by  contact 
beds,  or  by  percolating  filters  ;  double-contact  beds  can  be  most 
strongly  recommended. 

According  to  Dibbin,  yeast  refuse  is  decomposed  very  well  in 
contact  beds  composed  of  slate. 

(14)  Sewage  from  the  manufacture  of  Sour -kr out. 

In  this  process  there  result  effluents  containing  large  amounts 
of  decomposable  substances,  which,  as  a  consequence  of  the 
sulphur  contained  in  the  cabbage,  undergo  decomposition 
accompanied  by  a  very  strong  smell. 

The  introduction  of  such  sewage  into  the  town  drains  is  danger- 
ous, as  good  purification  of  the  whole  of  the  town's  sewerage  is 
then  brought  into  the  question. 

There  is  no  information  as  yet  with  regard  to  the  direct  puri- 
fication of  the  sewage,  but  in  my  opinion  the  effluents  would  be 
similar  in  character  to  those  from  dairies,  and  should  be  purified 
therefore  in  a  corresponding  manner. 

In  certain  places  the  sewage  is  purified  successfully  by  allowing 
it  to  trickle  through  deep  pits. 

(15)  Sewage  from  Dye  Works  (Print  Works). 

More  or  less  large  amounts  of  organic  colouring  matter  are 
always  found  in  this  type  of  sewage,  which  is,  consequently, 


124  SEWAGE   DISPOSAL 

always  coloured.  The  opinion  was  formerly  held  that  the  colour 
of  the  sewage  caused  little  harm  to  the  stream  receiving  it,  that, 
on  the  contrary,  coloured  effluents  had  an  aesthetic  value  in  that 
they  allowed  the  waters  of  the  stream  to  be  coloured  with  all  the 
colours  of  the  rainbow  over  considerable  distances. 

A  research  of  Tienemann  of  very  recent  date  has,  however, 
shown  that  this  view  is  not  quite  correct.  On  the  contrary,  many 
colouring  matters  used  in  the  manufacture  of  paper,  although 
they  are  not  poisonous  at  all  to  men,  have  a  strongly  poisonous 
action,  even  at  great  dilutions,  on  the  most  varied  kinds  of 
organisms  present  in  water.  Victoria  blue,  methyl  violet,  char- 
coal-black, and  diamond  green  B  have  proved  especially  fatal  to 
fresh-water  organisms  even  at  very  great  dilutions,  so  that 
sewage  containing  these  colours  may  be  very  harmful  to  the  fish 
in  the  river.  This  may  arise  from  direct  destruction  of  the  fish 
or  from  the  destruction  of  the  lower  organisms  in  the  water, 
whereby  the  source  of  the  fishes'  livelihood  is  either  ruined  or 
impaired.  Besides  colouring  matters  this  sewage  often  contains 
mordants  (mainly  aluminium,  ferric  and  zinc  salts). 

The  removal  of  colouring  matters  from  sewage  is  still  an  un- 
solved problem.  The  difficulty  of  removing  the  colour  increases 
the  more  permanent  the  colours  are.  By  biological  means, 
whether  by  land  treatment  or  by  the  artificial  biological  process, 
the  colour  is  only  incompletely  removed.  The  surface  of  the 
land  or  the  beds  is  gradually  saturated  with  the  colouring 
matter,  and  then  allows  further  quantities  to  pass  through  un- 
changed. 

Partial  decolorisation  is  attained  in  the  case  of  many  dye- 
stuffs  by  chemical  precipitation,  using  sulphate  of  iron  and  lime. 
After  precipitation  the  sewage  is  passed  through  sedimentation 
tanks  or  filtered  by  means  of  mechanical  filters. 

The  following  is  a  method  of  decolorisation  which  has  come 
into  general  use  :  The  dye-stuffs  are  reduced  to  the  leuco  base  and 
then  the  colourless  sewage  is  run  away.  The  process  cannot  be 
recommended,  however.  The  leuco  bases  are  again  oxidised  in 
the  river  and  give  coloured  compounds,  taking  from  the  river- 
water  the  oxygen  necessary  for  the  oxidation  process.  In  this 
way,  therefore,  not  only  do  the  colours  reappear  in  the  river,  but, 
in  addition,  the  removal  of  the  oxygen  from  the  river-water 
causes  the  harm  done  to  the  river  to  be  greater  and  more  serious. 


PURIFICATION   OF   INDUSTRIAL   SEWAGE 

It  should  be  best  to  dilute  such  sewage  considerably,  and  then 
run  it  into  the  town's  sewers. 


(16)  Sewage  from  Chemical  Works. 

Sewage  from  chemical  works  varies  so  greatly  according  to  the 
class  of  wrork  that  it  is  impossible  to  give  a  definite  mode  of 
purification  ;  indeed,  this  is  all  the  more  true  as  the  methods  of 
manufacture  are  frequently  kept  strictly  secret.  Generally 
speaking,  it  may  be  said  of  this  class  of  sewage  that  suspended 
matter  may  be  removed  in  sedimentation  tanks.  Substances 
which  are  lighter  than  water  (tar,  oil,  etc.)  can  be  removed  from 
the  sewage  by  means  of  grease  separators. 

Nearly  all  chemical  processes  require  acids  or  alkalies.  By 
mixing  acid  and  alkaline  effluents  sufficient  neutralisation  is 
attained  in  some  cases.  Acids  are  generally  neutralised  with 
lime. 

Large  amounts  of  Glauber's  salt  often  result  from  neutralisa- 
tion processes.  The  effluents  from  organic  dye  works  are  often 
very  rich  in  this  salt.  In  general  these  salts  should  be  harmless 
to  the  living  matter  in  the  river,  but  I  might  point  out  that  such 
sewage,  in  my  experience,  is  capable  of  destroying  extremely 
rapidly  sedimentation  tanks  made  of  concrete.  These  data, 
which  I  found  in  the  course  of  quite  different  investigations,  were 
confirmed  by  a  manager  of  a  large  dye  works.  The  destruction 
results  from  the  conversion  of  the  free  lime  of  the  concrete  into 
gypsum  by  means  of  the  Glauber's  salt.  This  is  accompanied  by 
a  disintegration  of  the  concrete. 

Very  many  chemical  processes  yield  coloured  effluents.  The 
previous  section  may  be  referred  to  for  their  purification. 

The  erection  of  reservoirs  can  be  strongly  recommended  for 
such  works,  as  the  sewage  is  sometimes  greatly  polluted  and  large 
in  amount,  while  at  other  times  it  is  less  polluted  and  in  much 
smaller  quantity. 

Occasionally  separate  treatment  of  the  individual  effluents 
can  be  recommended.  In  other  cases  mixing  will  be  advantage- 
ous, as  the  dissolved  substances  may  precipitate  one  another. 
All  these  circumstances,  and,  in  general,  the  best  methods  of 
purification  for  sewage  from  chemical  works,  are  determined  in 
practice  by  experiment. 


126  SEWAGE   DISPOSAL 

(17)  Sewage  from  Bleach  Works. 

In  bleach  works,  sewage  is  formed  which  contains  alkaline  and 
acid  boiler  liquors  in  addition  to  chloride  of  lime.  The  most 
harmful  are  the  alkali  boiler  liquors.  According  to  Schiele, 
superficial  purification  can  be  attained  thus  :  The  alkaline  liquors 
are  stored  up  in  reservoirs,  the  acid  liquors  are  gradually  mixed 
with  them,  and  then  the  whole  is  clarified  in  settling  tanks.  The 
sewage  so  purified  can  then  be  further  treated  in  biological  plants. 
According  to  a  patent  process,  Keller  (Stuttgart)  makes  the 
alkaline  boiler  liquors  applicable  anew,  as  he  adds  dissolved  or 
undissolved  lime  to  them  with  constant  stirring,  by  which  the 
solution  assumes  a  brighter  colour.  The  liquid  decanted  from 
the  lime  is  then  used  again  as  it  is,  or  concentrated  in  some  way 
or  another. 

(18)  Sewage  from  Gas  Works. 

Sewage  from  gas  plants  is  generally  chocolate-brown  in  colour, 
has  an  obnoxious  odour,  and  contains  free  alkali,  sulphocyanides, 
phenol,  cyanides,  tarry  products,  etc.  The  disposal  of  such 
sewage  is  a  matter  of  great  difficulty,  owing  to  the  poisonous 
substances  present.  Its  admixture  with  the  town's  sewage 
makes  purification  of  the  latter  considerably  more  difficult,  if 
there  are  in  any  way  considerable  amounts  of  sewage  from  the 
gas  plant. 

Chemical  precipitation  followed  by  sedimentation  is  one  method 
of  treatment,  not,  however,  very  effective. 

Radcliffe  has  worked  out  and  tested  a  process  which  proceeds 
as  follows  :  First,  the  suspended  lime  is  removed  in  settling 
tanks,  then  the  water  is  pumped  into  a  fractionating  apparatus, 
allowed  to  trickle  down  over  plates,  whilst  from  below  hot  ex- 
haust gases  containing  carbon  dioxide  and  air  are  blown  in. 
The  dissolved  lime  is  thus  precipitated  and  the  phenols  are 
destroyed.  The  lime  is  separated  off  in  a  tank,  and  the  liquid  is 
then  driven  into  a  fractionating  plant,  serving  as  an  auxiliary  to 
the  first.  Here  a  stronger  stream  of  air  removes  the  phenols  and 
other  substances.  They  are  led  into  a  furnace  and  burnt.  The 
sulphocyanides  are  decomposed  by  dropping  in  sulphuric  acid. 
After  passing  through  a  second  settling  tank  and  then  being 
filtered  over  coke  the  water  should  be  quite  clear.  In  St.  Albans, 


PURIFICATION   OF   INDUSTRIAL   SEWAGE        127 

England,  such  a  plant  is  used.  Many  well-known  English  sewage 
experts  have  tested  the  process  and  expressed  themselves  favour- 
ably with  regard  to  it. 

If  gas-works  effluents  are  to  be  purified  by  the  biological 
process  they  must  be  greatly  diluted.  Even  after  considerable 
dilution  or  admixture  with  domestic  sewage,  the  beds  may  not 
be  loaded  too  greatly  with  sewage  if  sufficient  purification  is  to 
be  obtained. 

(19)  Sewage  from  Ammonia  Works. 

This  sewage  is  characterised  by  a  high  content  of  mineral  and 
organic  substances.  It  contains  calcium  chloride  and  free  lime, 
under  certain  circumstances  calcium  sulphydrate  and  free  sulphur ; 
of  organic  substances,  tarry  matter,  thiocyanates,  pyridine  bases, 
phenol,  and  other  substances  are  present. 

The  free  caustic  lime  can  be  removed  by  allowing  the  sewage 
to  trickle  over  inclined  planes,  whereby  it  is  converted  into 
calcium  carbonate. 

By  adding  caustic  soda  (i  to  2  Ib.  per  10,000  gallons  of  sewage) 
the  sulphur,  which  is  often  present  in  a  finely  divided  condition, 
should  be  precipitated  along  with  the  calcium  carbonate  which 
has  separated  out.  Sulphocyanides  are  generally  present  in 
small  amounts,  but  may  amount  to  i  per  cent.  Such  large 
quantities  can  be  precipitated  with  copper  salts  and  further 
recovered. 

(20)  Sewage  from  Potash  Works. 

Sewage  from  potash  works  contains  inorganic  salts  in  large 
amounts,  especially  magnesium  and  calcium  chlorides.  Such 
sewage  cannot  be  purified  by  the  usual  methods.  It  is  gener- 
ally conveyed  directly  to  the  river,  and  frequently  considerably 
increases  the  hardness  of  the  river-water  and  the  quantity  of 
salts  that  it  contains.  This  may  be  very  unpleasant  from  the 
point  of  view  of  health  if  towns  situated  lower  down  the  river 
draw  their  drinking-water  from  the  river  concerned. 

The  Imperial  Health  Commission  of  Germany  has  been  occu- 
pied with  the  question  of  this  type  of  sewage.  It  recommends 
that  the  limit  be  fixed  at  an  increase  to  50°  of  hardness  in  the 
river-water.  Further,  the  following  procedure  was  recommended 


128  SEWAGE    DISPOSAL 

to  prevent  the  river-water  receiving  excessive  amounts  of  such 
salts  :— 

(1)  Arrangement  of  suitable  distributors  and  regulation  of 
the  discharge  in  the  case  of  the  final  liquors. 

(2)  Provision  of  reservoirs  large  enough  to  contain  the  final 
liquors  in  individual  works. 

(3)  A  number  of  controls  working  through  a  central  enquiry 
office. 

Lately  these  effluents  have  been  used  for  laying  dust  on  the 
roads.  Owing  to  the  calcium  and  magnesium  chlorides  present, 
which  are  very  hygroscopic  salts,  the  sewage  keeps  roads  moist 
and  thus  lays  the  dust.  In  Frankfort,  with  such  liquors,  it  has 
been  shown  by  investigation  that  they  are  specially  useful  in 
winter  during  a  dry  frost.  On  such  days  the  streets  cannot  be 
watered,  as  they  would  very  soon  freeze.  Each  watering-cart  set 
in  motion  on  the  unwatered  streets  generates  big  clouds  of  fine 
ice  particles.  If,  however,  the  streets  are  sprayed  with  these 
liquors,  owing  to  their  considerably  lower  freezing-point,  not  only 
is  no  ice  formed,  but  the  surface  of  the  street  (asphalt)  remains 
moist  for  eight  days  without  requiring  further  watering. 

(21)  Sewage  from  Metal  Works  and  works  manufacturing 

Mordants. 

Such  sewage  is  generally  acid  and  contains  metallic  salts.  It 
is  very  harmful  if  led  directly  to  the  river.  It  discolours  the 
river-water,  moreover,  owing  to  the  separation  of  iron  and  other 
metallic  salts. 

Purification  can  be  effected  by  neutralisation  with  lime  and 
subsequent  treatment  in  settling  tanks.  One  disadvantage  of 
this  process  is  that  it  yields  large  amounts  of  sludge. 

It  is  better,  therefore,  to  evaporate  the  effluents  and  recover  the 
metallic  salts.  In  England,  according  to  Schiele,  it  pays  to  use 
this  method. 

(22)  Sewage  from  works  manufacturing  Photographic  Paper 

and  Cards. 

The  sewage  from  such  concerns  can  be  divided  into  two  classes, 
concentrated  sewage  and  washing-waters.  The  concentrated 


PURIFICATION   OF   INDUSTRIAL   SEWAGE        129 

effluents  contain  the  most  diverse  chemicals  (acids,  alkalis,  etc.), 
as  must  naturally  occur  in  such  manufacturing  operations. 

Pritzkow  recommends  either  leading  the  concentrated  effluent 
directly  into  sewers,  in  which  case  difficulties  should  not  arise,  or 
the  effluent  should  receive  a  special  treatment.  Pritzkow 
advises  the  following  method  of  purification  :  The  strongly 
concentrated  sewage  (dyeing  machines  ;  the  working  up  of  the 
residues)  is  freed  from  acids,  alkalis,  and  harmful  salts  by 
methods  worked  out  from  individual  tests.  To  take  one  example, 
it  would  perhaps  pay  to  recover  thiosulphate  from  the  water 
containing  it.  Then  the  water  thus  obtained,  and  the  concen- 
trated effluent,  with  which  such  treatment  is  impossible,  are 
collected  in  a  tank.  Here  the  various  kinds  of  sewage  can  mix, 
decompose,  and,  as  far  as  possible,  neutralise  one  another.  The 
discharge  from  this  tank  might  be  mixed  with  the  washing-waters, 
which  are  freed  from  suspended  matter  in  a  special  sedimentation 
tank,  and  can  then  be  run  away  into  the  river. 

(23)  Sewage  containing  Cyanides. 

This  type  of  sewage  has  been  the  object  of  an  enquiry  by  the 
Imperial  Health  Commission  (Reichsgesundheitsrates)  (Rubner 
and  von  Buchka).  Many  sugar  refineries  work  up  their  molasses 
for  cyanides.  Gases  from  smelting  furnaces  are  often  freed  from 
their  impurities  by  washing  with  water,  and  are  then  used  again 
in  the  process.  The  sewage  resulting  from  this  washing  process 
generally  contains  large  amounts  of  cyanides.  In  the  sugar 
.refinery  at  Dessau,  according  to  the  description  of  the  Imperial 
Health  Commission,  the  cyanides  are  removed  from  the  sewage 
in  the  following  manner  :  The  effluents  containing  cyanides  are 
collected  in  pits.  Sacks  containing  sulphate  of  iron  are  hung  in 
the  water,  and  the  salt  dissolved  by  the  hot  sewage.  Then  caustic 
soda  is  added,  and  it  is  next  made  weakly  acid  with  sulphuric 
acid.  The  whole  is  well  stirred  by  blowing  in  a  rapid  current  of 
air.  The  addition  of  caustic  soda  and  sulphuric  acid  is  made  in 
calculated  amounts  corresponding  to  the  analytical  results  from 
tests  of  the  contents  of  the  pits.  The  mixture  thus  obtained  is 
then  expressed  in  filter-presses.  Should  the  water  from  the 
presses  not  be  clear,  or  if  the  qualitative  test  (Prussian  blue)  still 
shows  the  presence  of  cyanides,  it  is  sent  back  to  the  pits,  and 


130  SEWAGE   DISPOSAL 

from  thence  back  once  more  to  the  presses.  The  blue  sludge, 
which  comes  from  the  presses  containing  about  70  per  cent  water, 
is  dried  in  pans  and  then  contains  about  45  per  cent  of  potassium 
ferrocyanide. 


(24)  Sewage  from  plants  employed  in  scouring,  combing,  and 
finishing  wool. 

The  most  concentrated  and  unpleasant  effluent  from  this 
manufacturing  process  is  the  effluent  from  the  scouring  of  the 
wool,  containing  soap.  It  is  to  be  recommended  that,  in  all 
circumstances,  such  sewage  should  be  worked  up  by  itself.  It 
is  generally  freed  from  the  threads  by  means  of  screens,  sieves, 
or  similar  apparatus,  and  is  then  acidified  with  sulphuric  acid  to 
decompose  the  soap.  Good  mixing  is  obtained  by  blowing  in  a 
rapid  current  of  air  or  steam.  The  acidified  sewage  is  then 
allowed  to  stand  for  a  time  in  large  settling  tanks.  The  sludge, 
which  is  rich  in  fats,  is  worked  up  for  fat  (see  p.  106).  The  sewage 
can  then  be  further  purified  by  means  of  intermittent  ground 
filtration,  or  by  the  artificial  biological  process  (percolating  filters 
or  double-contact  beds  being  the  best).  The  small  amount  of  free 
sulphuric  acid  should  not  occasion  any  trouble  in  the  biological 
treatment.  In  some  plants,  however,  the  acid  effluent  is  neu- 
tralised with  lime  before  the  biological  process.  Frequently  the 
sewage  is  conveyed  directly  to  the  river  without  any  biological 
treatment,  after  acidification  with  sulphuric  acid  and  sedimenta- 
tion. 

(25)  Sewage  from  Petroleum  Refineries. 

The  sewage  resulting  from  the  refining  process  consists  of 
waste  acid,  acid  washing-water,  caustic  soda,  and  alkaline  wash- 
waters.  According  to  a  decree  of  the  authorities  in  Austria,  the 
disposal  of  such  sewage  is  to  be  effected  somewhat  in  the  following 
manner  :  The  waste  acid  is  allowed  to  stand  some  time,  during 
which  the  tar  separates  out  on  top  ;  this  can  be  skimmed  off  and 
burned  (mixed  with  sawdust),  or  it  is  worked  up  as  asphalt. 
The  dirty  and  dilute  acid  may  be  sold  to  artificial-manure  manu- 
facturers. If  the  acid  cannot  be  sold  it  is  neutralised  with  lime  ; 
the  resinous  mass  thus  separating  out  is  skimmed  off,  and  the 


PURIFICATION   OF   INDUSTRIAL   SEWAGE        131 

neutralised  effluent  is  freed  from  suspended  material,  oily,  tarry, 
and  such  substances,  both  in  settling  tanks  and  by  filtration 
through  wool- waste  or  peat,  etc. 

The  acid  and  alkaline  washing-waters  are  mixed  ;  if  the  acid 
is  not  sufficient  to  neutralise  the  alkaline  portion,  part  of  the 
muddy  acid  from  above  (after  the  removal  of  the  resinous  mass) 
is  added  to  the  mixture.  This  mixture  should  still  have  a  dis- 
tinctly acid  reaction ;  it  is  then  boiled  to  decompose  the  petroleum 
soaps.  After  skimming  off  the  oily  layer  on  top,  the  aqueous 
and  still  acid  liquid  underneath  is  also  purified  in  the  above- 
mentioned  settling  tanks  and  filters. 

For  larger  works  a  special  clarification  plant  for  acid  and 
alkaline  sewage  is  to  be  recommended. 

(26)  Sewage  containing  Soaps. 

If  it  is  a  question  of  an  effluent  containing  soap  without  the 
addition  of  other  polluted  water,  as  is  the  case  with  many 
laundries,  good  purification  can  be  effected,  according  to  Heydt, 
in  clarifying  wells  having  large  plates  to  oppose  the  passage  of  the 
sewage,  which  is  made  to  flow  at  a  very  small  velocity.  Milk  of 
lime  is  automatically  added  to  the  sewage  at  the  inlet  to  the 
well.  The  amount  added  must  be  estimated  by  experiments 
on  the  particular  effluent.  After  passing  through  a  sand  filter 
of  small  depth  the  sewage  is  sufficiently  purified  for  it  to  be  led 
without  harm  to  any  small  stream.  It  is  important  to  take  care 
that  the  floating  particles  which  are  formed  are  retained  in  the 
clarifying  plant  and  do  not  reach  the  filter.  It  is  advantageous 
to  have  the  sewage  exposed  suitably  to  the  air  (to  absorb  carbon 
dioxide)  before  coming  on  to  the  filter,  and  to  interpose  a 
reservoir  or  second  clarifying  well. 

Use  of  septic  tanks  for  this  class  of  sewage  is  considered  in- 
advisable by  Heydt,  and  only  a  biological  plant  with  a  very  large 
surface  is  practicable.  Lubbert  also  regards  the  biological 
process  for  the  purification  of  laundry  sewage  as  unsuitable,  and 
likewise  recommends  precipitation  with  lime. 

In  the  opinion  of  the  author  it  must  be  possible  to  purify  such 
soapy  liquors  by  the  addition  of  sulphuric  acid  till  weakly  acid, 
followed  by  the  separation  in  a  grease  separator  of  the  precipi- 
tated fatty  acids,  which  could  then  be  recovered.  The  fatty 


132  SEWAGE   DISPOSAL 

acids  would  be  separated  all  the  more  easily,  as  such  sewage 
generally  reaches  the  sewers  warm. 

(27)  Sewage  from  Oil  Works. 

The  sewage,  on  account  of  its  high  content  of  organic  sub- 
stances, was  used  in  South  France  as  manure  for  pasture-land. 
Its  success,  however,  was  very  small.  The  reason  for  this  is,  no 
doubt,  the  large  amount  of  acid  in  the  sewage.  According  to 
Ventre,  the  sewage  should  lose  its  acidity  on  standing  in  the  air, 
and  then  after  mixing  with  superphosphate  or  with  animal 
manure  it  should  give  a  good  manurial  material. 

G.    The  Disinfection  of  Sewage. 

Sewage  generally  has  a  germ-number  of  one  or  more  millions. 
As  Spitta  has  shown,  most  of  the  bacteria  are  associated  with  the 
undissolved  matter,  so  that  by  separating  off  the  suspensions  a 
considerable  reduction  of  the  germs  is  effected.  The  bulk  of  these 
bacteria  are  of  a  harmless  nature,  but  there  are  undoubtedly 
also  many  disease  germs  among  them. 

Since  these  disease  germs  under  ordinary  circumstances  can 
only  exist  a  limited  time  in  the  river  under  the  changed  and 
hostile  conditions  there,  disinfection  of  the  sewage  is  generally 
unnecessary,  the  more  so  as  nowadays  river-water  is  no  longer 
used  by  municipalities  for  the  water  supply  without  undergoing 
some  treatment. 

It  is  naturally  very  advisable  in  this  state  of  affairs  that  the 
excreta  from  people  suffering  from  all  infectious  diseases,  espe- 
cially typhoid,  should  be  disinfected.  The  Prussian  law  takes 
this  into  account,  since  it  prescribes  disinfection  of  all  the  refuse 
from  persons  suffering  from  notifiable  diseases. 

It  is  best,  likewise,  to  disinfect  the  sewage  of  houses  where  there 
is  sickness,  before  it  enters  the  general  sewage  system. 

Disinfection  is  necessary  in  times  of  epidemic,  as  the  many 
disease  germs  deposited  in  the  river  favour  the  spreading  of 
contagion.  In  most  sewage  plants  there  are  for  cases  such  as 
these  devices  which  disinfect  the  whole  of  the  sewage.  Chloride 
of  lime  has  proved  the  best  disinfectant,  but  this  only  acts 
sufficiently  well  when  all  suspended  matter  over  i  millimetre 


DISINFECTION   OF   SEWAGE 

in  size  has  been  removed.  According  to  Schmidt mann,  Thumm, 
and  Reichle,  in  times  of  epidemic  the  storm  overflow-water  of  the 
town  constitutes  an  especial  danger. 

Industrial  sewage  in  general  need  not  be  disinfected.  Only 
in  the  sewage  from  slaughter-houses  and  knackers'  yards  can 
disease  germs  be  present.  Tannery  sewage  also  may  contain 
inflammatory  spores.  Chloride  of  lime  is  the  best  disinfectant 
for  such  sewage  also. 

According  to  Kurpjuweit,  good  regulations  for  the  amount  of 
chloride  of  lime  required  cannot  be  given.  In  general,  treatment 
for  two  hours  is  sufficient.  With  a  concentration  of  I  part  of 
chloride  of  lime  in  5000  parts  of  water,  and  with  treatment  lasting 
two  hours,  Kurpjuweit  was  able  to  disinfect  the  sewage  in  Char- 
lottenburg  sufficiently. 

On  the  contrary,  Kranepuhl  asserts  that  for  certainty  a  con- 
centration of  i :  1000  must  be  employed  for  two  hours'  treatment, 
or  a  concentration  of  i  :  2000  for  four  hours. 


LIST  OF   AUTHORS 


A 

Abraham  and  Marmier,  20 

Agga,  32 

Ardern,  112 

Arnold  and  Schirmer,  42 

B 

Baudet,  10 
Becker,  35 
Bell,  ii 
Berkefeld,  43 
Bieske,  32 
Bischoff,  30 
Bitter,  14 
Blacher,  59,  6 1 
Blunt,  27 
Bock,  33 
Bollmann,  33 
Braikowitz,  16 
Breda,  11,  33 
Brettschneider,  89 
Breyer,  42 
von  Buchka,  129 
Buhring,  33 
Bujard,  108 
Biittner,  33 
Bujwid,  29 

C 

Candy,  n 

Chamberland,  42 

Chemischen   Fabriken  fiir  Laboratori- 

umsbedarf,  61 
Chlopin,  22 

Continental  Co.,  German,  45 
Courmont,  27,  28 
Craven,  26 
Cronheim,  96 

D 

Degener,  84,  109 
Dehne,  33,  55 
Deseniss  and  Jacobi,  49 


Dibbin,  123 

Dietrich,  121 

Dobrowolski,  22 

Dolezalek,  22 

Dost,  108 

Downes,  27 

Dunbar,  49,  79,  89,  90,  119 

Duyk,  24 


Erlwein,  22,  28 
von  Esmarch,  41,  45 


Fiddian,  88 
Fischer,  32 
Fliigge,  30 
Fowler,  112 
Frankel,  9,  30 
Frankland,  90,  94 
Freund,  76 
Friedberger,  14 
Friihling,  68,  94 


Gartner,  23,  42 

Gehrke,  121 

Gesellschaft  fiir  Abwasserklarung,  73 

Gottschlich,  13,  14 

Gotze,  9 

Grimm,  28,  29 

Grosze-Bohle,  75 

Grove,  45 

Griinanger,  121 

Guth,  119 


H 


Halbertsma,  22 
Halvor,  11 
Harm,  119 
Helm,  33 


135 


136 

Henneking,  95,  96 
Herzfeld,  121 
Hess,  33 
Hesse,  42 
Heydt,  131 
Heyer,  37,  38 
Hilgermann,  13,  17 
Hofer,  97 
Howatson,  20,  24 
Hoyermann,  121,  122 
Humboldt,  55 


Imhoff,  25,  29,  100 
Imhoff-Lagemarm,  114 

J 

Jensen  and  Co.,  42 
Jewell,  ii,  13,  14,  33 
Johnson,  25,  29 

K 

Kaibel,  73 
Keller,  126 
Kimberley,  114,  119 
Konig,  6,  8,  9,  44 
Koerting,  32 
Kranepuhl,  133 
Kremer,  71,  72,  73 
Kremer- Schilling,  73 
Kressling,  48 
Krohnke,  n,  32 
Kurpjuweit,  133 
Kurth,  32 


Lahmeyerwerke,  48 
Lanz,  32 

Lautenschlager,  43 
Lehmann,  113 
Lepsius,  76 
von  der  Linde,  33 
Logau,  117 
Lubbert,  131 
Liihrig,  35 


Markwart,  121 
ter  Mer,  101,  107 


X 


LIST   OF   AUTHORS 


Mertens,  120 
Mezger,  i 
Middledorf,  82 
Miquel,  10 
Mouchet,  10 


Neiszer,  30,  48 
Nobel,  91 
Nogier,  27 
Noll,  35 
Novak,  i 


Oesten,  32 
Ohlmiiller,  22 
Olschewski,  42 
Otto,  21 
Otto  and  Vosmaer,  20 


Pape  and  Henneberg,  45 
Pasteur  Institute,  22 
Permutit  Filter  Co.,  61 
Pfeiffer,  32 
Piefke,  8,  31,  32,  42 
de  Plato,  122 
Prall,  22 
Pritzkow,  129 
Proskauer,  22,  48 
Pue'ch,  ii 
Puech-Chabal,  9 

Q 
Quartz  Lamp  Co.,  28,  29 

R 

Radcliffe,  126 

Reeves,  ii 

Reichle,  84,  101,  108,  109,  113,  118, 

Reichling,  32 

Reisert,  33,  53,  55,  59 

Richert,  15,  1 6 

Rideal,  23 

Rien,  70 

Rimman,  117 

Ritschel  and  Henneberg,  46 

Rubner,  129 


LIST   OF   LOCALITIES 


137 


Sauna,  23 

Saville,  25,  29 

Schafer,  101,  107 

Schaffer  and  Walcker,  45 

Scheelhaase,  15,  37 

Schick,  97 

Schiele,  24,  25,  76,  77,  78,  86,  87,  89, 

9°,  92,  93,  105,  108,  126,  128 
Schmidt,  43 

Schmidtmann,  84,  nS,  133 
Schmidt  and  Sons,  46 
Schone,  121 

Schreiber,  13,  22,  23,  51 
Schuder,  22 
Schwers,  32,  33 
Sellenscheidt,  33 
Siemens  and  Co.,  45 
Siemens  and  Halske,  20,  28,  47,  48 
Sjolemma,  113,  114 
Spillner,  82,  100,  102 
Spitta,  132 
Stadtereinigung  und   Ingenierbau,   73, 

ii5 
Sucro,  ii 


Taacks,  32 
Thiel,  121 
Thiem,  15,  32 


Tienemann,  124 

Thiesing,  101,  120 

Thumm,  24,  25,  84,  109,  133 

Travis,  79,  89 

Trindall,  20 


U 


Uhlfelder,  69 
Ultra- Violet,  29 


Ventre,  132 
Vincey,  17 
Vogelsang,  72 
Volger,  i 
Voran,  33,  55 


W 


Walker,  26 

Warren,  n 

Wehner,  40 

Wehrenpfennig,  55 

Weldert,  28,  29,  104,  in 

Wellensiek,  121,  122 

Westinghouse,  Cooper,  Hewitt  Co.,  29 

Wingen,  32 


Zahn,  113,  122,  123 


Alexandria,  14 
Alleringersleben,  121 
Altona,  9 


LIST  OF  LOCALITIES 


Chateaudun,  10 
Chemnitz,  16 
Cologne,  55,  75,  76 
Constantinople,  64 


Belfast,  103 

Berlin,  31,  42,  43,  45,  61,  73,  94, 

Bochum,  100 

Bradford,  105 

Breslau,  35,  94 

Brunswick,  16,  94 

Bury,  1 08 


Celle,  43 
Charlottenburg,  51,  133 


D 


Darmstadt,  73 
115  Delitzsch,  31 

Dessau,  38,  45,  129 
Dortmund,  94 
Dresden,  70 

£ 

!    Eduardsfeld,  91 
:    Elberfeld,  69 

Elbing,  31 
I    Essen,  N.W.,  100 


138 


INDEX   OF   SUBJECTS 


Frankfort-on-Maine,  15,  33,  37,  48,  51, 
55.  69,  74.  75.  76>  97.  98,  99,  101,  102, 
106,  107,  128 

Freiburg,  94 


Gerhden,  121 
Gelsenkirchen,  30 
Gothenburg,  16 
Gottingen,  100 


H 


Halle  a.  S.,  55,  114 
Hamburg,  9,  17,  42,  45 
Hanau,  28,  29 
Hanover,  101 
Harburg,  101 
Hermannstadt,  20 


Ichenhausen,  97 


K 


Kalk,  55 
Kassel,  100,  106 
Kiel,  1 20 
Konigsberg,  9,  14 
Kopenick,  109 
Kutzenberg,  97 


Lawrence,  94 
London,  5,  103 


M 

Magdeburg,  94,  121 
Manchester,  89,  103 
Middlekerke,  24,  25 
Minneapolis,  26 

N 

Niederdodeleben,  121 
Nizza,  20 
Norwich,  79 

O 

Offenbach,  16 
Ohama,  26 


Paderborn,  20,  22,  120 
Paris,  17,  20,  23,  29 
Pforzheim,  108 
Posen,  33,  91 

R 

Recklinghausen,  100 


Salford,  103 
Schweinfurt,  16 
St.  Albans,  126 
St.  Mans,  20 
St.  Petersburg,  20,  22 
Sternberg,  31 
Stuttgart,  126 
Swinemiinde,  120 

W 

Warsaw,  9 
Weinding,  97 
Wiesbaden,  73,  115 
Wismar,  31 


INDEX   OF  SUBJECTS 


Aeration  of  water  to  remove  carbon 

dioxide,  38 
Algae,  65 
Alluvial  soil,  30 

Ammonia  works,  sewage  from,  127 
Apparatus  for  adding  chemicals,  38,  77 
boiling  drinking-water,  45 


Arsenic,  118,  119 
Asbestos  niters,  42 
Assimilation,  65 


Bacteria,  2,  3,  17,  18,  22,  23,  28,  31,  41 

45,  48,  63,  132 
—  anaerobic,  78 


INDEX   OF   SUBJECTS 


139 


Bacteria,  destruction  of,  3 

—  pathogenic,   10,  22,  25,   28,  45,  92, 
132 

Bacterial  decomposition,  66 

Bacterium  coli,  28,  48 

Bank  filtration,  natural,  15 

Baryta  process  of  water  softening,  59 

— -  —  advantages,  disadvantages,  59 

Bastard  pump  of  Deseniss  and  Jacobi, 

49 

—  purification,  51 
Baths,  river,  64 
Bed  irrigation,  91 
Beds,  biological,  85 

—  distribution  of  water,  87 

—  impregnation  permissible,  87 

—  layer  of  slime  on,  86 

—  material  for,  85 

—  protection  against  cold,  87 
Beet,  wash  waters,  120 
Biological  process,  artificial,  85 

—  cost  of,  89 
—  nature  of,  89 

—  purification  of  sewage,  85 
Bleach  works  effluents,  126 
Boiler  corrosion,  59,  61 

—  fire  clinkers,  112 

—  scale,  52 

•  preventatives,  61 

—  sludge,  52 

—  water,  corrosive  action,  58 
Boiling,  the,  of  drinking-water,  45 

—  advantages  and  disadvantages, 47 
Breslau  water  calamity,  35 
Breweries,  sewage  from,  117,  118 
Bromine,  18 


Calcium  hydrate,  54 

—  permanganate,  18 

—  sulphydrate,  127 
Carbolic  sulphuric  acid,  30 
Carbonic  acid  removal,  36,  52 
Cardboard  works  sewage,  113 
Cascade  for  removal  of  air,  19,  22 
Cellulose  works,  sewage  from,  115,  116, 

117. 

Central  water  supply,  40 
Centrifuge   Schafer-ter-Mer,    101,   102, 

103 


Chamberland  Filter,  42 
Charcoal  filters,  41 
Chemicals,  action  of,  76 

—  addition  of,  10,  76 

—  disadvantages,  77 

—  mode  of  addition,  77 
— •  quantities  added,  77 
Chemical  works  sewage,  125 
Chloride  of  lime,  18,  132 

—  process   for  sterilising   drink- 
ing-water, 25 
Chlorine,  18 

Cholera,  2,  17,  22,  45,  64 
Chrome  iron  alum,  18 
Chromium  salts,  118 
Ciliata,  65 
Clarifying  tanks,  4,  74 

—  arrangement  of  the  tank  bed,  74 

—  towers,  74 

—  wells,  74,  79 
Clay  filters,  42 

Clinkers  from  refuse  destructors,  85 
Cloth  factories,  sewage,  113 
Coal-pulp  process,  84 

—  gasification  of  sludge,  108 

—  sludge,  114 
Coke,  86 

Coke  aerators,  33 

Coli  bacteria,  28,  48 

Colour,  removal  of,  from  water,  13,  1 8 

Coloured  effluents,  112,  118 

Condenser  waters,  no,  116,  120 

Contact  beds,  86 

—  advantages,  disadvantages,  88 

—  choking  of,  with  sludge,  88 

—  distribution  of  water  on  to,  87 

—  single  and  double,  86 

—  size  of  material  for,  86 
Cooling  waters,  no 
Copper  chloride,  18 

Cost  of  all  water-purification  processes, 
29 

—  biological  processes,  89 

—  chloride  of  lime  process,  25 

—  intermittent  sand  filtration,  96 

—  mechanical  filtration,  18 

—  ozone  process,  23 

—  removal  of  iron,  34 

—  manganese,  36 
•  sand  filtration,  9 


140 


INDEX    OF   SUBJECTS 


Cost  of  sewage  farming,  94 

—  sludge  disposal,  104 

—  ultra-violet  light  process,  29 
Cyanides,  113,  126 

Cyanides,  sewage  containing,  129,  130 

D 

Dairy  effluents,  119 
Dams,  3 

De  Chlor  process,  26 
Destructors,  refuse,  108 

—  clinkers  from,  85 
Diarrhoea  germs,  2,  22 

Diff users,  effluents  from,  120,  121 
Diluvial  soil,  30 
Disease  germs,  2,  25,  63,  133 
Disinfection  of  sewage,  132,  133 

—  water-mains  and  wells,  30 
Disposal  and  profit  from  sludge  resi- 
dues, 97         % 

Distilleries,  sewage  from,  123 
Double  filtration,  Gotze,  9 
Drinking-water  purification,  2 

in  other  directions  than  health, 

30 

—  on  large  scale,  4 

—  on  small  scale,  40 
Drying  of  sludge  (see  Sludge) 
Dunbar  Filters,  49 
Dust-laying  with  sewage,  in,  128 
Dye  works  sewage,  123,  124 


Eduardsfeld  process,  91 

Elbe  water,  1 7 

Emscher  wells,  82 

Emulsifiers,  21 

England,  sewage  disposal,  85 

Epidemic,  17 


Ferric  chloride,  18 

process,  24 

Fibrous  material,  recovery  of,  115 

Fiddian  sprinklers,  88 

Filter,  in,  114,  131 

—  film,  8,  1 1 

— •  film  in  biological  processes,  89 

Filtration,  4 


Filtration  pressure,  7 

—  velocity,  6,  8,  10,  n,  14 
Fish  life,  harm  to,  64,  124 

—  ponds,  sewage  disposal  through,  96 
Flies,  plague  of,  88 

Floating    material    in    sedimentation 

tanks,  76 
Fungi,  formation  of,  116 


Gas  works,  sewage  from,  126,  127 

Glue  liquors,  120 

Granulation  works,  sewage  from,   114 

Gratings,  68 

Grease  in  sludge,  98 

—  recovery,  105,  106,  107 
—  separators,  72 

Grit  chambers,  73 
Grit-chamber  residues,  97 
composition  of,  97 

—  drying  of,  98 

H 

Hampton  doctrine,  89 
Hardness  of  water,  52 

—  degrees  of,  English,  French,  German, 
52 

—  due  to  chlorides,  60 

—  gypsum,  59 

—  nitrates,  60 

—  permanent,  52,  53,  59 

—  temporary,  52,  53,  54,  59 
Havel,  85 
Hops  and  grain  drying,  sewage  from, 

117 

Hose  irrigation,  91 
Household  filters,  41 
Howatson  Filter,  20,  24 
Hum-in  process    (Hoyermann  and 

Wellensiek),  121 
Hydrogen  peroxide,  18,  27 

I 

Industrial  sewage  for  dust-laying,  in 
—  purification  of,  109 

—  by  chemical  precipitation,  109 

—  by   combination    of   different 
effluents,  in 

reception  into  the  drainage  sys- 
tem, 109 


INDEX    OF   SUBJECTS 


141 


Industrial  sewage,  reservoirs  for,  1 1 1 

Infiltration,  14 

Infusoria,  65 

Intermittent  sand  filtration,  94 

—  cost,  96 

—  depth  of  filter  layer,  95 

—  doses,  95 

—  drainage,  95 

—  filter  beds,  95 

—  nature  of  soil,  95 

—  periods  of  rest,  95 

—  preliminary  treatment,  95 

—  purifying  action,  96 
Irrigation,  infiltration,  91 

—  rude  or  surface,  91 
Iron  bacteria,  31 

—  colloidal,  31 

J 

Jewell  Mechanical  Filter,  1 1 


K 

Kalmann  formula,  54 

Kieselguhr  Filters,  43 

Knackers'  yards,  sewage  from,  120 

Kremer  apparatus,  71 

—  septic  well,  73 


Land  irrigation,  90 

Lime,  18 

Lime-soda  softening  process,  55 

Liming  process,  effluents  from,  118 

Liquefying  chamber,  82 


M 

Magma  Filter,  112 

Maine  River  water,  15,  51,  66 

Malting  liquors  from  breweries,  117 

Manganese,  removal  of,  35 

Manure,  98,  104,  105,  114,  132 

—  artificial,  105 

Margarine  works,  sewage  from,  119 

Mechanical  filtration,    10,    n,    13,    17, 

114,  124 

--  purification  of  sewage,  68 
Mercury-vapour  lamps,  27,  28,  29 
Metal  works,  sewage  from,  128 


Mines  (coal- washing)  effluents,  114 
Mordants,  124 

—  sewage  from  manufactories  of,  128 

N 

Naphthalene,  118 

Neutralisation  of  drinking-water,  36 

—  plant,  Frankfort,  39 
Neva,  20 

Nitrogen,  90,  98,  104,  105 
Nobel  treatment,  91 

O 

Oil,  sewage  containing,  113 

—  works  sewage,  132 
Ozone,  18,  20,  21,  22,  23 

—  concentration,  21 

—  plant,  St.  Petersburg,  20 

—  plants,  small,  47 

—  stationary,  47 

—  transportable,  47 


Paper  works  sewage,  115 
Percolating  filters,  86 

—  advantages    and    disadvantages, 
88 

—  distribution  of  sewage  on  to,  87 

—  subsequent    purification    of    ef- 
fluent, 89 

Permutit,  35 

—  process,  60 

—  advantages    and    disadvantages, 
60 

Petroleum  refineries,  sewage  from,  130 

Phenol,  127 

Phosphoric  acid,  90,  98,  105 

Photographic  papers,  sewage  from,  129 

Plague  of  flies,  88 

Plankton,  artificial,  n 

Porcelain  filters,  42 

Potash,  90,  98 

—  works,  sewage  from,  127 
Potato  wash  waters,  122 

j    Poudrette,  105 
Preliminary  filtration  (Puech-Chabal), 

9 

—  purification,  85 

1    Press  waters,  116,  120,  121 


142 


INDEX   OF   SUBJECTS 


Prufungsanstalt,  Konigl.  fur  Wasser- 
versorgung  und  Abwasserbeseiti- 
gung,  22,  28 

Prussian  blue,  113 

Ptomaines,  2 

Pumps,  sump,  74 

Purification  of  domestic  sewage,  67 

—  industrial  sewage,  109 

—  drinking-water,  2 

—  for  technical  purposes,   51 

—  in  other  directions  than  of 
health,  30 

—  on  large  scale,  4 

—  on  small  scale,  40 
Pyridine  bases,  127 

Q 

Quartz  lamps,  27,  28,  29 

R 

Rakes,  69 

—  coarse,  69 

—  residues  from,  97 

—  drying  of,  97 

water  content  of,  98 

Recovery  of  fibrous  material,  115 
Removal  of  iron,  30 

—  action,  34 

—  for  industrial  purposes,  32 

—  from  single  wells,  49 

—  plants  for  open  and  closed,  34 

—  systems  for,  32 
Reservoirs,  in 
Resinous  masses,  130 
Revolving  sprinklers,  88 
Rien  Sieve,  70 

River  baths,  64 

—  bed,  mud  upon,  66 

—  pollution,  63,  64,  65 

—  water,  3,  15,  63,  64,  66 

—  application     to     technical     pur- 
poses, 64 

—  capacity  for  absorbing  acid,  66 
Rotatoria,  65 

Ruhr  Talsperren  Co.,  16 

S 
Sand  filters,  5,  15 

—  covered,  uncovered,  7 

—  filter  layer,  7,  8 
percolating,  10 


Sand  filters,  period  of  running,  8 

—  washing,  8 

—  filtration,  double  (Gotze),  9 

—  natural,  15 

—  preliminary  (Puech-Chabal),  9 

—  slow,  5,  1 6 
Screens,  68 

Scum  on  septic-tank  sewage,  78 
Sedimentation  tanks,  4,  74 

—  (Patent  Imhoff-Lagemann)  ,114 
Self -purification  of  rivers,  65 

Septic  tanks,  78,  79 
Sewage  disposal,  97 

—  domestic,  67 

—  industrial,  109 

—  purification  by  fish-ponds,  96 
Sewage  farms,  90 

—  bed  irrigation,  91 

—  cost,  94 

—  drainage,  91 

—  impregnation  permissible,  93 

—  periods  of  rest,  93 

—  preliminary  purification,  92 

—  rents  from,  94 

—  suitable  produce,  92 

—  surface  treatment,  90 
Sieves,  69 

Sieve  waters,  116 
Slaughter-house  effluents,  120 
Sludge    centrifuges    (Schafer-ter-Mer), 
101 

—  composition  of,  98,  99 

—  deposits,  99 

—  covering  material  for,  99 

—  disinfection  of,  99 

—  destruction  by  burning,  108 

—  disposal,  76,  83,  97 

by  addition  of  saltpetre,  104 

by  sinking  in  the  sea,  102 

in  Frankfort,  107 

—  drying  by  admixture  with  refuse, 
100 

—  burial,  100 

—  drainage,  100 

—  electro-osmose,   102 

—  filtration,  99 

—  Magma  Filter,  112 

—  cost,  104 

—  on  the  land,  99 

—  Emscher  well,  83,  100 


INDEX   OF   SUBJECTS 


143 


Sludge,  fresh,  100 

—  from     effluents     from     percolating 
niters,  97 

—  septic  tanks,  100 

—  grease  content,  99 

—  experiments    in    recovery    of, 
in  Frankfort,  106 

—  grease  recovery,  105 

—  in  Bradford,  105 

—  in  Kassel,  105 

—  pumps  under  water,  83 

—  vessels,  103 

Small  niters  used  in  technical  work,  42 
Smells,  trouble  from,  88,  98,  99,  107, 

118 

Smelting  furnaces,  sewage  from,  129 
Soap  in  sewage,  113,  131 
Sodium  hydrate,  54 

—  hypochlorite,  25 

—  sulphide,  118 

—  thiosulphate,  118 

Softening  of  boiler-feed  waters,  52 

—  formula  for  calculating  the  addition 
required,  54 

-  with  baryta,  59 

—  lime-soda,  55 

—  advantages      and      disadvan- 
tages, 58 

—  permutit,  60 

Softening  plant,  Voran  system,  56 

Sour-krout,  123 

Spores,  inflammatory,  133 

Spree,  85 

Spring  water,  i 

Staphylococcus,  44,  48 

Starch  works,  sewage  from,  122 

Sterilisation,  processes  of  water,  18 

—  towers  (Ozone  process),  21,  22 
Stone  filters,  42 

Strawboard  works  sewage,  114 

Sugar  refineries,  sewage  from,  120,  121, 

122 
Sulphite  cellulosersewage  from,'ji5 


Sulphocyanides,  127 

Superheated      steam      for     sterilising 

wells,  30 
Surface  treatment  in  sewage  farming, 

9i 
—  waters,  i,  2,  3,  14,  15,  63,  64 


Tannery  sewage,  112,  118,  133 

Tar,  127,  130 

Travis  wells,  79 

Turbidity,  removal  of,  13,  18,  41 

Typhoid,  2,  22,  45,  132 

—  bacilli,  10 

—  disease,  17 

—  epidemic,  30 

—  mortality,  1 7 

U 

Uhlfelder's  revolving  screen,  69 
Ultra-violet  apparatus,  .small,  48 
rays,  27 

V 

Vacuum  process  for  removing  carbon 
dioxide  from  water,  40 

W 

Wagner  suction  apparatus  for  sludge 

removal,  83 

Weights  and  measures,  table  of,  xiv 
Weston  Controller,  1 1 
Wool  scouring,  combing,  and  finishing, 

sewage  from,  130 
Works  clarification  plants,  109 

—  sewage  in  detail,  no 


Yeast  works,  sewage  from,  123 

Z 

Zeoliths,  60 


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Bruce,  E.  M.     Pure  Food  Tests i2mo,  *i  25 

Bruhns,  Dr.     New  Manual  of  Logarithms 8vo,  half  morocco,  2  oo 

Brunner,  R.     Manufacture  of  Lubricants,  Shoe  Polishes  and  Leather 

Dressings.     Trans,  by  C.  Salter 8vo,  *3  oo 

Buel,  R.  H.    Safety  Valves.     (Science  Series  No.  21.) i6mo,  o  50 

Bulman,  H.  F.,  and  Redmayne,  R.  S.  A.     Colliery  Working  and  Manage- 
ment  8vo,  6  oo 

Burgh,  N.  P.     Modern  Marine  Engineering 4to,  half  morocco,  10  oo 

Burstall,  F.  W.    Energy  Diagram  for  Gas.    With  Text 8vo,  150 

Diagram.    Sold  separately *i  oo 

Burt,  W.  A.     Key  to  the  Solar  Compass i6mo,  leather,  2  50 

Burton,  F.  G.     Engineering  Estimates  and  Cost  Accounts ' I2mo,  *i  50 

Buskett,  E.  W.     Fire  Assaying I2mo,  *i  25 

Butler,  H.  J.     Motor  Bodies  and  Chassis 8vo,  *2  50 

Byers,  H.  G.,  and  Knight,  H.  G.    Notes  on  Qualitative  Analysis 8vo,  *i  50 

Cain,  W.     Brief  Course  in  the  Calculus i2mo,  *i  75 

Elastic  Arches.     (Science  Series  No.  48.) i6mo,  o  50 

Maximum  Stresses.     (Science  Series  No.  38.) i6mo,  o  50 

Practical  Designing  Retaining  of  Walls.     (Science  Series  No.  3.) 

i6mo,  o  50 
Theory     of     Steel-concrete    Arches   and    of    Vaulted    Structures. 

(Science  Series  No.  42.) i6mo,  o  50 

Theory  of  Voussoir  Arches.     (Science  Series  No.  12.) i6mo,  o  50 

Symbolic  Algebra.     (Science  Series  No.  73.) i6mo,  o  50 

Campin,  F.     The  Construction  of  Iron  Roofs 8vo,  2  oo 

Carpenter,  F.  D.    Geographical  Surveying.     (Science  Series  No.  37.) .  1 6mo, 
Carpenter,    R.   C.,  and  Diederichs,  H.     Internal  Combustion  Engines. 

8vo,  *s  oo 

Carter,  E.  T.    Motive  Power  and  Gearing  for  Electrical  Machinery  . .  8vo,  *5  oo 

Carter,  H.  A.     Ramie  (Rhea),  China  Grass i2mo,  *2  oo 

Carter,  H.  R.     Modern  Flax,  Hemp,  and  Jute  Spinning. 8vo,  *3  oo 

Cathcart,  W.  L.     Machine  Design.     Part  I.  Fastenings 8vo,  *3  oo 

Cathcart,  W.  L.,  and  Chaff ee,  J.  I.     Elements  of  Graphic  Statics 8vo,  *3  oo 

Short  Course  in  Graphics i2mo,  i  50 

Caven,  R.  M.,  and  Lander,  G.  D.     Systematic  Inorganic  Chemistry .  i2mo,  *2  oo 

Chalkley,  A.  P.    Diesel  Engines 8vo,  *3  oo 

Chambers'  Mathematical  Tables 8vo,  i  75 

Charnock,  G.  F.     Workshop  Practice.     (Westminster  Series.). .  .  .8vo  (In  Press.} 

Charpentier,  P.     Timber 8vo,  *6  oo 

Chatley,  H.     Principles  and  Designs  of  Aeroplanes.    (Science   Series.) 

No.  126.) i6mo,  o  50 

How  to  Use  Water  Power i2mo,  *i  oo 

Gyrostatic  Balancing 8vo,  *i  oo 

Child,  C.  D.    Electric  Arc 8vo,   *(7n  Press.) 


D.  VAN  NOSTRAND  COMPANY'S  SHORT  TITLE   CATALOG       7 

Child,  C.  T.    The  How  and  Why  of  Electricity i2mo,  i  oo 

Christie,  W.  W.     Boiler- waters,  Scale,  Corrosion,  Foaming 8vo,  *3  oo 

Chimney  Design  and  Theory 8vo,  *3  oo 

Furnace  Draft.     (Science  Series  No.  123.) i6mo,  o  50 

Water:  Its  Purification  and  Use  in  the  Industries 8vo,  *2  oo 

Church's  Laboratory  Guide.     Rewritten  by  Edward  Kinch 8vo,  *2  50 

Clapperton,  G.     Practical  Papermaking , 8vo,  2  50 

Clark,  A.  G.    Motor  Car  Engineering. 

Vol.  I.     Construction *3  oo 

Vol.  II.    Design (In  Press.} 

Clark,  C.  H.     Marine  Gas  Engines i2mo,  *i  50 

Clark,  D.  K.     Rules,  Tables  and  Data  for  Mechanical  Engineers 8vo,  5  oo 

Fuel:  Its  Combustion  and  Economy i2mo,  T  50 

The  Mechanical  Engineer's  Pocketbook '. i6mo,  2  oo 

Tramways:  Their  Construction  and  Working 8vo,  5  oo 

Clark,  J.  M.     New  System  of  Laying  Out  Railway  Turnouts i2mo,  I  oo 

Clausen-Thue,  W.     ABC  Telegraphic  Code.     Fourth  Edition i2mo,  *5  oo 

Fifth  Edition 8vo,  *7  oo 

The  A  i  Telegraphic  Code 8vo,  *y  50 

Cleemann,  T.  M.     The  Railroad  Engineer's  Practice i2mo,  *i  50 

Clerk,  D.,  and  Idell,  F.  E.     Theory  of  the  Gas  Engine.     (Science  Series 

No.  62.) i6mo,  o  50 

Clevenger,  S.  R.     Treatise   on   the   Method   of  Government   Surveying. 

i6mo,  morocco 2  50 

Clouth,  F.     Rubber,  Gutta-Percha,  and  Balata 8vo,  *s  oo 

Cochran,  J.    Treatise  on  Cement  Specifications 8vo,  *i  oo 

Coffin,  J.  H.  C.     Navigation  and  Nautical  Astronomy i2mo,  *3  50 

Colburn,  Z.,  and  Thurston,  R.  H.     Steam  Boiler  Explosions.     (Science 

Series  No.  2.) i6mo,  o  50 

Cole,  R.  S.    Treatise  on  Photographic  Optics i2mo,  i  50 

Coles-Finch,  W.     Water,  Its  Origin  and  Use 8vo,  *5  oo 

Collins,  J.  E.     Useful  Alloys  and  Memoranda  for  Goldsmiths,  Jewelers. 

i6mo o  50 

Constantine,    E.     Marine  Engineers,  Their    Qualifications   and   Duties. 

8vo,  *2  oo 

Coombs,  H.  A.     Gear  Teeth.     (Science  Series  No.  120.) i6mo,  o  50 

Cooper,  W.  R.     Primary  Batteries 8vo,  *4  oo 

"  The  Electrician  "  Primers . . . ' 8vo,  *5  oo 

Part  I *i  50 

Part  II *2  50 

Part  III *2  oo 

Copperthwaite,  W.  C.     Tunnel  Shields. 4to,  *p  oo 

Corey,  H.  T.     Water  Supply  Engineering 8vo  (In  Press.) 

Corfield,  W.  H.     Dwelling  Houses.     (Science  Series  No.  50.) i6mo,  o  50 

Water  and  Water-Supply.     (Science  Scries  No.  17.) i6mo,  o  50 

Cornwall,  H.  B.     Manual  of  Blow-pipe  Analysis 8vo,  *2  50 

Courtney,  C.  F.     Masonry  Dams 8vo,  3  50 

Cowell,  W.  B.     Pure  Air,  Ozone,  and  Water I2mo,  *2  oo 

Craig,  T.     Motion  of  a  Solid  in  a  Fuel.     (Science  Series  No.  49.) ....  i6mo,  o  50 

Wave  and  Vortex  Motion.     (Science  Series  No.  43.) i6mo,  o  50 

Cramp,  W.     Continuous  Current  Machine  Design 8vo,  *2  50 


8        D.  VAN   NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG 

Crocker,  F.  B.     Electric  Lighting.     Two  Volumes.     8vo. 

Vol.   I.     The  Generating  Plant ,. 3  oo 

Vol.  II.     Distributing  Systems  and  Lamps 3  oo 

Crocker,  F.  B.,  and  Arendt,  M.     Electric  Motors 8vo,  *2  50 

Crocker,  F.  B.,  and  Wheeler,  S.  S.    The  Management  of  Electrical  Ma- 
chinery  i2tno,  *i  oo 

Cross,  C,  F.,  Sevan,  E,  J.,  and  Sindall,  R,  W.     Wood  Pulp  and  Its  Applica- 
tions.    (Westminster  Series.) 8vo,  *2  oo 

Crosskey,  L.  R,     Elementary  Perspective 8vo,  i  oo 

Crosskey,  L,  R.,  and  Thaw,  J.    Advanced  Perspective 8vo,  i  50 

Culley,  J,  L.      Theory  of  Arches.     (Science  Series  No,  87.) i6mo,  o  50 

Dadourian,  H.  M.     Analytical  Mechanics i2mo,  (In  Press.) 

Davenport,  C.     The  Book,     (Westminster  Series.) 8vo,  *2  oo 

Da  vies,  D.  C.     Metalliferous  Minerals  and  Mining 8vo,  5  oo 

Earthy  Minerals  and  Mining 8vo,  5  oc 

Davies,  E.  H.     Machinery  for  Metalliferous  Mines 8vo,  8  oo 

Da  vies,  F.  H.     Electric  Power  and  Traction 8vo,  *2  oo 

Foundations  and  Machinery  Fixing.     (Installation  Manual  Series.) 

i6mo,  (In  Press.) 

Dawson,  P.    Electric  Traction  on  Railways 8vo,  *g  oo 

Day,  C.    The  Indicator  and  Its  Diagrams i2mo,  *2  oo 

Deerr,  N.    Sugar  and  the  Sugar  Cane 8vo,  *8  oo 

Deite,  C.     Manual  of  Soapmaking.     Trans,  by  S.  T.  King 4to,  *5  oo 

De  la  Coux,  H.     The  Industrial  Uses  of  Water.     Trans,  by  A.  Morris. 

8vo,  *4  50 

Del  Mar,  W.  A.    Electric  Power  Conductors 8vo,  *2  oo 

Denny,  G.  A.     Deep-level  Mines  of  the  Rand 4to,  *io  oo 

Diamond  Drilling  for  Gold *5  oo 

De  Roos,  J.  D.  C.    Linkages.     (Science  Series  No.  47.) i6mo,  o  50 

Derr,  W.  L.     Block  Signal  Operation Oblong  i2mo,  *i  50 

Maintenance-of-Way  Engineering (In  Preparation.) 

Desaint,  A.     Three  Hundred  Shades  and  How  to  Mix  Them 8vo,  *io  oo 

De  Varona,  A,     Sewer  Gases.     (Science  Series  No.  55.) i6mo,  o  50 

Devey,  R,  G.    Mill  and  Factory  Wiring.     (Installation  Manuals  Series.) 

i2mo,  *i  oo 

Dibdin,  W.  J.     Public  Lighting  by  Gas  and  Electricity 8vo,  *8  oo 

Purification  of  Sewage  and  Water 8vo,  6  50 

Dichmann,  Carl.    Basic  Open-Hearth  Steel  Process I2mo,  *3  50 

Dieterich,  K.     Analysis  of  Resins,  Balsams,  and  Gum  Resins 8vo,  *3  oo 

Dinger,  Lieut.  H.  C.     Care  and  Operation  of  Naval  Machinery i2mo,  *2  oo 

Dixon,  D.  B.     Machinist's  and  Steam  Engineer's  Practical  Calculator. 

i6mo,  morocco,  i  25 

Doble,  W.  A.     Power  Plant  Construction  on  the  Pacific  Coast  (In  Press.) 
Dodd,  G.     Dictionary    of    Manufactures,    Mining,    Machinery,    and    the 

Industrial  Arts i2mo,  i  50 

Dorr,  B.  F.     The  Surveyor's  Guide  and  Pocket  Table-book. 

i6mo,  morocco,  2  oo 

Down,  P.  B.     Handy  Copper  Wire  Table i6mo,  *i  oo 

Draper,  C,  H.    Elementary  Text-book  of  Light,  Heat  and  Sound. . .  i2mo,  i  oo 
Heat  and  the  Principles  of  Thermo-dynamics i2mo,  i  50 


D.   VAN  NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG        9 

Duckwall,  E.  W.     Canning  and  Preserving  of  Food  Products 8vo,  *s  oo 

Dumesny,  P.,  and  Noyer,  J.     Wood  Products,  Distillates,  and  Extracts. 

8vo,  *4  50 
Duncan,  W.  G.,  and  Penman,  D.     The  Electrical  Equipment  of  Collieries. 

8vo,  *4  oo 
Dunstan,  A.  E.,  and  Thole,  F.  B.  T.    Textbook  of  Practical  Chemistry. 

i2mo,  *i  40 

Duthie,  A.  L.     Decorative  Glass  Processes.     (Westminster  Series.).  .8vo,  *2  oo 

Dwight,  H.  B.    Transmission  Line  Formulas 8vo,   (In  Press.) 

Dyson,  S.  S.     Practical  Testing  of  Raw  Materials 8vo,  *s  oo 

Dyson,  S.  S.,  and  Clarkson,  S.  S.    Chemical  Works 8vo,  *7  50 

Eccles,  R.  G.,  and  Duckwall,  E.  W.     Food  Preservatives 8vo,  paper  o  50 

Eddy,  H.  T.     Researches  in  Graphical  Statics 8vo,  i  50 

Maximum  Stresses  under  Concentrated  Loads 8vo,  i  50 

Edgcumbe,  K.     Industrial  Electrical  Measuring  Instruments 8vo,  *2  50 

Eissler,  M.     The  Metallurgy  of  Gold 8vo,  7  50 

The  Hydrometallurgy  of  Copper. 8vo,  *4  50 

The  Metallurgy  of  Silver 8vo,  4  oo 

The  Metallurgy  of  Argentiferous  Lead 8vo,  5  oo 

Cyanide  Process  for  the  Extraction  of  Gold 8vo,  3  oo 

A  Handbook  on  Modern  Explosives 8vo,  5  oo 

Ekin,  T.  C.     Water  Pipe  and  Sewage  Discharge  Diagrams folio,  *3  oo 

Eliot,  C.  W.,  and  Storer,  F.  H.     Compendious  Manual  of  Qualitative 

Chemical  Analysis I2mo,  *i  25 

Elliot,  Major  G.  H.     European  Light-house  Systems 8vo,  5  oo 

Ennis,  Wm.  D.    Linseed  Oil  and  Other  Seed  Oils 8vo,  *4  oo 

Applied  Thermodynamics 8vo  *4  50 

Flying  Machines  To-day 12010,  *i  50 

Vapors  for  Heat  Engines i2mo,  *i  oo 

Erfurt,  J.     Dyeing  of  Paper  Pulp.     Trans,  by  J.  Hubner 8vo,  *y  50 

Ermen,  W.  F.  A.     Materials  Used  in  Sizing 8vo,  *2  oo 

Erskine-Murray,  J.     A  Handbook  of  Wireless  Telegraphy 8vo,  *3  50 

Evans,  C.  A.     Macadamized  Roads (In  Press.) 

Ewing,  A.  J.     Magnetic  Induction  in  Iron 8vo,  *4  oo 

Fairie,  J.     Notes  on  Lead  Ores I2mo,  *i  oo 

Notes  on  Pottery  Clays i2mo,  *i  50 

Fairley,  W.,  and  Andre,  Geo.  J.     Ventilation  of  Coal  Mines.     (Science 

Series  No.  58.) i6mo,  o  50 

Fairweather,  W.  C.     Foreign  and  Colonial  Patent  Laws 8vo,  *3  oo 

Fanning,  J.  T.     Hydraulic  and  Water-supply  Engineering 8vo,  *s  oo 

Fauth,  P.      The  Moon  in  Modern  Astronomy.     Trans,  by  J.  McCabe. 

8vo,  *2  oo 

Fay,  I.  W.     The  Coal-tar  Colors 8vo,  *4  oo 

Fernbach,  R.  L.     Glue  and  Gelatine 8vo,  *3  oo 

Chemical  Aspects  of  Silk  Manufacture I2mo,  *i  oo 

Fischer,  E.     The  Preparation  of  Organic  Compounds.     Trans,  by  R.  V. 

Stanford I2mo,  *i  25 

Fish,  J.  C.  L.     Lettering  of  Working  Drawings Oblong  8vo,  i  oo 

Fisher,  H.  K.  C.,  and  Darby,  W.  C.     Submarine  Cable  Testing 8vo,  *3  50 


10     D.  VAN   NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG 

Fiske,  Lieut.  B.  A.     Electricity  in  Theory  and  Practice 8vo,  2  50 

Fleischmann,  W.     The   Book  of  the  Dairy.     Trans,  by  C.  M.  Aikman. 

8vo,  4  oo 
Fleming,  J.  A.     The  Alternate-current  Transformer.     Two  Volumes.    8vo. 

Vol.    I.     The  Induction  of  Electric  Currents *5  oo 

Vol.  II.     The  Utilization  of  Induced  Currents *5  oo 

Propagation  of  Electric  Currents 8vo,  *3  oo 

Centenary  of  the  Electrical  Current 8vo,  *o  50 

Electric  Lamps  and  Electric  Lighting 8vo,  *3  oo 

Electrical  Laboratory  Notes  and  Forms 4to,  *5  oo 

A  Handbook  for  the  Electrical  Laboratory  and  Testing  Room.     Two 

Volumes 8vo,  each,  *5  oo 

Fleury,  P.    Preparation  and  Uses  of  White  Zinc  Paints 8vo,  *2  50 

Fluery,  H.     The  Calculus  Without  Limits  or  Infinitesimals.     Trans,  by 

C.  O.  Mailloux (In  Press.) 

Flynn,  P.  J.     Flow  of  Water.     (Science  Series  No.  84.) i6mo,  o  50 

Hydraulic  Tables.     (Science  Series  No.  66.) i6mo,  o  50 

Foley,  N.     British  and  American  Customary  and  Metric  Measures,  .folio,  *3  oo 
Foster,  H.  A.    Electrical  Engineers'  Pocket-book.     (Sixth  Edition.) 

i2mo,  leather,  5  oo 

Engineering  Valuation  of  Public  Utilities  and  Factories 8vo,  *3  oo 

Foster,  Gen.  J.  G.     Submarine  Blasting  in  Boston  (Mass.)  Harbor. . .  .  4to,  3  50 

Fowle,  F.  F.     Overhead  Transmission  Line  Crossings i2mo,  *i  50 

The  Solution  of  Alternating  Current  Problems 8vo  (In  Press.) 

Fox,  W.  G.    Transition  Curves.     (Science  Series  No.  no.) i6mo,  o  50 

Fox,  W.,  and  Thomas,  C.  W.     Practical  Course  in  Mechanical  Draw- 
ing  i2mo,  i  25 

Foye,  J.  C.     Chemical  Problems.     (Science  Series  No.  69.) i6mo,  o  50 

Handbook  of  Mineralogy.     (Science  Series  No.  86.) i6mo,  o  50 

Francis,  J.  B.     Lowell  Hydraulic  Experiments 4to,  15  oo 

Freudemacher,    P.    W.    Electrical    Mining    Installations.     (Installation 

Manuals  Series-) i2mo,  *i  oo 

Frith,  J.    Alternating  Current  Design 8vo,  *2  oo 

Fritsch,  J.    Manufacture  of  Chemical  Manures.    Trans,  by  D.  Grant. 

8vo,  *4  oo 

Frye,  A.  I.     Civil  Engineers'  Pocket-book i2mo,  leather,  *5  oo 

Fuller,  G.  W.      Investigations  into  the  Purification  of  the  Ohio  River. 

4to.  *io  oo 

Furnell,  J.     Paints,  Colors,  Oils,  and  Varnishes 8vo,  *i  oo 

Gairdner,  J.  W.  I.    Earthwork 8vo,  (In  Press.) 

Gant,  L.  W.     Elements  of  Electric  Traction 8vo,  *2  50 

Garcia,  A.  J.  R.  V.     Spanish-English  Railway  Terms 8vo,  *4  50 

Garforth,  W.  E.     Rules  for  Recovering  Coal  Mines  after  Explosions  and 

Fires i2mo,  leather,  i  50 

Gaudard,  J.     Foundations.     (Science  Series  No.  34.) i6mo,  o  So 

Gear,  H.  B.,  and  Williams,  P.  F.     Electric  Central  Station  Distribution 

Systems 8vo,  *3  oo 

Geerligs,  H.  C.  P.     Cane  Sugar  and  Its  Manufacture 8vo,  *s  oo 

World's  Cane  Sugar  Industry .' 8vo,  *5  oo 

Geikie,  J.     Structural  and  Field  Geology 8vo,  *4  oo 


D.  VAN    NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG      11 

Gerber,  N.   Analysis  of  Milk,  Condensed  Milk,  and  Infants' Milk-Food.    8vo,  i  25 
Gerhard,  W.  P.     Sanitation,  Watersupply  and  Sewage  Disposal  of  Country 

Houses i2mo,  *2  oo 

Gas  Lighting.     (Science  Series  No.  in.) i6mo,  o  50 

Household  Wastes.     (Science  Series  No.  97.) i6mo,  o  50 

House  Drainage.     (Science  Series  No.  63.) i6mo,  o  50 

Sanitary  Drainage  of  Buildings.     (Science  Series  No.  93.) i6mo,  o  50 

Gerhardi,  C.  W.  H.     Electricity  Meters 8vo,  *4  oo 

Geschwind,   L.     Manufacture   of  Alum  and  Sulphates.     Trans,   by  C. 

Salter 8vo,  *s  oo 

Gibbs,  W.  E.     Lighting  by  Acetylene i2mo,  *i  50 

Physics  of  Solids  and  Fluids.     (Carnegie  Technical  School's  Text- 
books.)    *i  50 

Gibson,  A.  H.     Hydraulics  and  Its  Application 8vo,  *5  oo 

Water  Hammer  in  Hydraulic  Pipe  Lines I2mo,  *2  oo 

Gilbreth,  F.  B.     Motion  Study I2mo,  *2  oo 

Primer  of  Scientific  Management i2mo,  *i  oo 

Gillmore,  Gen.  Q.  A.     Limes,  Hydraulic  Cements  acd  Mortars 8vo,  4  oo 

Roads,  Streets,  and  Pavements I2mo,  2  oo 

Golding,  H.  A.     The  Theta-Phi  Diagram I2mo,  *i  25 

Goldschmidt,  R.     Alternating  Current  Commutator  Motor 8vo,  *3  oo 

Goodchild,  W.     Precious  Stones.     (Westminster  Series.) 8vo,  *2  oo 

Goodeve,  T.  M.     Textbook  on  the  Steam-engine i2mo,  2  oo 

Gore,  G.     Electrolytic  Separation  of  Metals 8vo,  *3  50 

Gould,  E.  S.     Arithmetic  of  the  Steam-engine I2mo,  i  oo 

Calculus.     (Science  Series  No.  112.) i6mo,  o  50 

High  Masonry  Dams.     (Science  Series  No.  22.) i6mo,  o  50 

Practical  Hydrostatics  and  Hydrostatic  Formulas.     (Science  Series 

No.  117.) i6mo,  o  50 

Grant,  J.     Brewing  and  Distilling.     (Westminster  Series.)  8vo  (In  Press.) 

Gratacap,  L.  P.     A  Popular  Guide  to  Minerals 8vo,  *3  oo 

Gray,  J.     Electrical  Influence  Machines I2mo,  2  oo 

Marine  Boiler  Design I2mo,  *i  25 

Greenhill,  G.     Dynamics  of  Mechanical  Flight 8vo,  *2  50 

Greenwood,  E.     Classified  Guide  to  Technical  and  Commercial  Books.  8vo,  *3  oo 

Gregorius,  R.     Mineral  Waxes.     Trans,  by  C.  Salter I2mo,  *3  oo 

Griffiths,  A.  B.     A  Treatise  on  Manures i2mo,  3  oo 

-  Dental  Metallurgy 8vo,  *3  50 

Gross,  E.     Hops 8vo,  *4  50 

Grossman,  J.     Ammonia  and  Its  Compounds I2mo,  *i  25 

Groth,  L.  A.     Welding  and  Cutting  Metals  by  Gases  or  Electricity 8vo,  *3  oo 

Grover,  F.     Modern  Gas  and  Oil  Engines 8vo,  *2  oo 

Gruner,  A.     Power-loom  Weaving 8vo,  *3  oo 

Gtildner,  Hugo,     internal  Combustion  Engines.     Trans,  by  H.  Diederichs. 

4to,  *io  oo 

Gunther,  C.  O.     Integration i2mo,  *i  25 

Gurden,  R.  L.     Traverse  Tables folio,  half  morocco,  *7  50 

Guy,  A.  E.     Experiments  on  the  Flexure  of  Beams .8vo,  *i  25 

Haeder,    H.      Handbook   on    the    Steam-engine.      Trans,  by  H.  H.  P. 

Powles i2mo,  3  oo 


00 

oo 
So 
50 
50 


12     D.  VAN   NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG 

Hainbach,  R.     Pottery  Decoration.     Trans,  by  C.  Slater i2mo,  *3  oo 

Haenig,  A.     Emery  and  Emery  Industry 8vo,  *2  50 

Hale,  W.  J.     Calculations  of  General  Chemistry I2mo,  *i  oo 

Hall,  C.  H.     Chemistry  of  Paints  and  Paint  Vehicles i2mo,  *2  oo 

Hall,  R.  H.     Governors  and  Governing  Mechanism i2mo,  *2  oo 

Hall,  W.  S.     Elements  of  the  Differential  and  Integral  Calculus 8vo,  *2  25 

Descriptive  Geometry 8vo  volume  and  a  4to  atlas,  *3  50 

Haller,  G.  F.,  and  Cunningham,  E.  T.     The  Tesla  Coil i2mo,  *i  25 

Halsey,  F.  A.     Slide  Valve  Gears i2mo,  i  50 

The  Use  of  the  Slide  Rule.     (Science  Series  No.  114.) i6mo,  o  50 

Worm  and  Spiral  Gearing.     (Science  Series  No.  116.). , i6mo,  o  50 

Hamilton,  W.  G.     Useful  Information  for  Railway  Men i6mo, 

Hammer,  W.  J.     Radium  and  Other  Radio-active  Substances 8vo,  * 

Hancock,  H.     Textbook  of  Mechanics  and  Hydrostatics 8vo, 

Hardy,  E.     Elementary  Principles  of  Graphic  Statics i2mo,  * 

Harrison,  W.  B.     The  Mechanics'  Tool-book I2mo, 

Hart,  J.  W.     External  Plumbing  Work 8vo,  *3  oo 

Hints  to  Plumbers  on  Joint  Wiping 8vo,  *3  oo 

Principles  of  Hot  Water  Supply 8vo,  *3  oo 

Sanitary  Plumbing  and  Drainage 8vo,  *3  oo 

Haskins,  C.  H.     The  Galvanometer  and  Its  Uses i6mo,  i  50 

Hatt,  J.  A.  H.     The  Colorist square  I2mo,  *i  50 

Hausbrand,  E.     Drying  by  Means  of  Air  and  Steam.     Trans,  by  A.  C. 

Wright i2mo,  *2  oo 

Evaporating,  Condensing  and  Cooling  Apparatus.     Trans,  by  A.  C. 

Wright 8vo,  *5  oo 

Hausner,  A.     Manufacture  of  Preserved  Foods  and  Sweetmeats.     Trans. 

by  A.  Morris  and  H.  Robson 8vo,  *3  oo 

Hawke,  W.  H.     Premier  Cipher  Telegraphic  Code 4to,  *5  oo 

100,000  Words  Supplement  to  the  Premier  Code 4to,  *5  oo 

Hawkesworth,  J.    Graphical  Handbook  for  Reinforced  Concrete  Design. 

4to,  *2  50 

Hay,  A.     Alternating  Currents 8vo,  *2  50 

Electrical  Distributing  Networks  and  Distributing  Lines 8vo,  *3  50 

Continuous  Current  Engineering 8vo,  *2  50 

Heap,  Major  D.  P.     Electrical  Appliances 8vo,  2  oo 

Heather,  H.  J.  S.     Electrical  Engineering 8vo,  *3  50 

Heaviside,  O.    Electromagnetic  Theory.      Vols.  I  and  n 8vo,  each,  *5  oo 

Vol.  IH 8vo,  *7  50 

Heck,  R.  C.  H.    The  Steam  Engine  and  Turbine 8vo,  *5  oo 

Steam-Engine  and  Other  Steam  Motors.    Two  Volumes. 

Vol.   I.     Thermodynamics  and  the  Mechanics 8vo,  *3  50 

Vol.  II.     Form,  Construction,  and  Working .^ 8vo,  *5  oo 

Notes  on  Elementary  Kinematics 8vo,  boards,  *i  oo 

Graphics  of  Machine  Forces 8vo,  boards,  *i  oo 

Hedges,  K.     Modern  Lightning  Conductors 8vo,  3  oo 

Heermann,  P.     Dyers'  Materials.     Trans,  by  A.  C.  Wright I2mo,  *2  50 

Hellot,  Macquer  and  D'Apligny.  Art  of  Dyeing  Wool,  Silk  and  Cotton.  8vo,  *2  oo 

Henrici,  O.     Skeleton  Structures 8vo,  i  50 

Hering,  D.  W.    Essentials  of  Physics  for  College  Students 8vo,  *i  60 

Hering-Shaw,  A.     Domestic  Sanitation  and  Plumbing.     Two  Vols. . .  8vo,  *5  oo 


D.  VAN   JSOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG      13 

Hering-Shaw,  A.    Elementary  Science 8vo,  *2  oo 

Herrmann,  G.    The  Graphical  Statics  of  Mechanism.    Trans,  by  A.  P. 

Smith ... ... i2mo,  2  oo 

Herzfeld,  J.    Testing  of  Yarns  and  Textile  Fabrics ^.  «.  «. .. ... .  .8vo,  *3  50 

Hildebrandt,  A.     Airships,  Past  and  Present , Svo,  *3  50 

Hildenbrand,  B.  W.    Cable-Making.     (Science  Series  No.  32.) i6mo,  o  50 

Hilditch,  T.  P.     A  Concise  History  of  Chemistry i2mo,  *i  25 

Hill,  J.  W.     The  Purification  of  Public  Water  Supplies.     New  Edition. 

(In  Press.) 

Interpretation  of  Water  Analysis (In  Press.) 

Hiroi,  I.     Plate  Girder  Construction.     (Science  Series  No.  95.) i6mo,  o  50 

Statically-Indeterminate  Stresses i2mo,  *2  oo 

Hirshfeld,  C.  F.     Engineering  Thermodynamics.     (Science  Series  No.  45.) 

i6mo,  o  50 

Hobart,  H.  M.     Heavy  Electrical  Engineering 8vo,  *4  50 

Design  of  Static  Transformers i2mo,  *2  oo 

Electricity Svo.,  *2  oo 

Electric  Trains Svo,  *2  50 

Hobart,  H.  M.    Electric  Propulsion  of  Ships Svo,  *2  oo 

Hobart,  J.  F.     Hard  Soldering>  Soft  Soldering  and  Brazing i2mo,  *i  oo 

Hobbs,  W.  R.  P.     The  Arithmetic  of  Electrical  Measurements i2mo,  o  50 

Hoff,  J.  N.     Paint  and  Varnish  Facts  and  Formulas i2ino,  *i  50 

Hoff,  Com.  W.  B.     The  Avoidance  of  Collisions  at  Sea. .  .  i6mo,  morocco,  o  75 

Hole,  W.     The  Distribution  of  Gas Svo,  *7  50 

Holley,  A.  L.     Railway  Practice folio,  12  oo 

Holmes,  A.  B.     The  Electric  Light  Popularly  Explained  ....  i2mo,  paper,  o  50 

Hopkins,  N.  M.     Experimental  Electrochemistry Svo,  *3  oo 

Model  Engines  and  Small  Boats 12010,  i  25 

Hopkinson,  J.     Shoolbred,  J.  N.,  and  Day,  R.  E.     Dynamic  Electricity. 

(Science  Series  No.  71.) i6mo,  o  50 

Horner,  J.     Engineers'  Turning Svo,  *3  50 

Metal  Turning I2ino,  i  50 

Toothed  Gearing i2mo,  2  25 

Houghton,  C.  E.     The  Elements  of  Mechanics  of  Materials i2mo,  *2  oo 

Houllevigue,  L.    The  Evolution  of  the  Sciences Svo,  *2  oo 

Houstoun,  R.  A.     Studies  in  Light  Production i2mo,  *2  oo 

Howe,  G.     Mathematics  for  the  Practical  Man i2mo,  *i  25 

Howorth,  J.     Repairing  and  Riveting  Glass,  China  and  Earthenware. 

Svo,  paper,  *o  50 

Hubbard,  E.     The  Utilization  of  Wood- waste Svo,  *2  50 

Hu'bner,  J.    Bleaching  and  Dyeing  of  Vegetable  and  Fibrous  Materials 

(Outlines  of  Industrial  Chemistry) Svo,  *5  oo 

Hudson,  O.  F.    Iron  and  Steel.     (Outlines  of  Industrial  Chemistry.) 

Svo,  (In  Press.) 

Humper,  W.     Calculation  of  Strains  in  Girders I2mo,  2  50 

Humphreys,  A.  C.    The  Business  Features  of  Engineering  Practice .  Svo,  *i  25 

Hunter,  A.    Bridge  Work Svo,  (In  Press.) 

Hurst,  G.  H.     Handbook  of  the  Theory  of  Color Svo,  *2  50 

Dictionary  of  Chemicals  and  Raw  Products Svo,  *3  oo 

Lubricating  Oils,  Fats  and  Greases Svo,  *4  oo 

Soaps Svo,  *s  oo 


14     D.  VAN  NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG 

Hurst,  G.  H.     Textile  Soaps  and  Oils 8vo,  *2  50 

Hurst,  H.  E.,  and  Lattey,  R.  T.    Text-book  of  Physics ,8vo,  *3  oo 

Also  published  in  three  parts. 

Part     I.  Dynamics  and  Heat *i  25 

Part   H.  Sound  and  Light *i  25 

Part  HI.  Magnetism  and  Electricity *i  50 

Hutchinson,  R.  W.,  Jr.     Long  Distance  Electric  Power  Transmission. 

i2mo,  *3  oo 

Hutchinson,  R.  W.,  Jr.,  and  Ihlseng,  M.  C.    Electricity  in  Mining. .  i2mo, 

(In  Press) 

Hutchinson,  W.  B.     Patents  and  How  to  Make  Money  Out  of  Them.  i2mo,  i  25 

Button,  W.  S.    Steam-boiler  Construction 8vo,  6  oo 

Practical  Engineer's  Handbook 8vo,  7  oo 

The  Works'  Manager's  Handbook 8vo,  6  oo 

Hyde,  E.  W.    Skew  Arches.     (Science  Series  No.  15.) i6mo,  o  50 

Induction  Coils.     (Science  Series  No.  53.) i6mo,  o  50 

Ingle,  H.     Manual  of  Agricultural  Chemistry 8vo,  *3  oo 

Innes,  C.  H.     Problems  in  Machine  Design I2mo,  *2  oo 

Air  Compressors  and  Blowing  Engines i2mo,  *2  oo 

Centrifugal  Pumps i2mo,  *2  oo 

The  Fan i2mo,  *2  oo 

Isherwood,  B.  F.     Engineering  Precedents  for  Steam  Machinery 8vo,  2  50 

Ivatts,  E.  B.     Railway  Management  at  Stations 8vo,  *2  50 

Jacob,  A.,  and  Gould,  E.  S.     On  the  Designing  and  Construction  of 

Storage  Reservoirs.     (Science  Series  No.  6.) i6mo,  o  50 

Jamieson,  A.     Text  Book  on  Steam  and  Steam  Engines 8vo,  3  oo 

Elementary  Manual  on  Steam  and  the  Steam  Engine i2mo,  i  50 

Jannettaz,  E.    Guide  to  the  Determination  of  Rocks.    Trans,  by  G.  W. 

Plympton I2mo,  i  50 

Jehl,  F.    Manufacture  of  Carbons 8vo,  *4  oo 

Jennings,  A.  S.     Commercial  Paints  and  Painting.     (Westminster  Series.) 

8vo  (In  Press.) 

Jennison,  F.  H.     The  Manufacture  of  Lake  Pigments .- 8vo,  *3  oo 

Jepson,  G.     Cams  and  the  Principles  of  their  Construction 8vo,  *i  50 

Mechanical  Drawing 8vo  (In  Preparation.) 

Jockin,  W.     Arithmetic  of  the  Gold  and  Silversmith i2mo,  *i  oo 

Johnson,  G.  L.     Photographic  Optics  and  Color  Photography 8vo,  *3  oo 

Johnson,  J.  H.      Arc  Lamps  and  Accessory  Apparatus.     (Installation 

Manuals  Series.) i2mo,  *o  75 

Johnson,   T.   M,      Ship    Wiring   and   Fitting.      (Installation    Manuals 

Series) i2mo,  *o  75 

Johnson,  W.  H.     The  Cultivation  and  Preparation  of  Para  Rubber ...  8 vo,  *3  oo 

Johnson,  W.  McA.     The  Metallurgy  of  Nickel (In  Preparation.) 

Johnston,  J.  F.  W.,  and  Cameron,  C.    Elements  of  Agricultural  Chemistry 

and  Geology I2mo,  2  60 

Joly,  J.     Raidoactivity  and  Geology i2mo,  *3  oo 

Jones,  H.  C.     Electrical  Nature  of  Matter  and  Radioactivity I2mo,  *2  oo 

Jones,  M.  W.     Testing  Raw  Materials  Used  in  Paint I2mo,  *2  oo 

Jones,  L.,  and  Scard,  F.  I.     Manufacture  of  Cane  Sugar 8vo,  *5  oc 


D.  VAN  NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG      15 

Jordan,  L.  C.    Practical  Railway  Spiral i2mo,  Leather,  *i  50 

Joynson,  F.  H.     Designing  and  Construction  of  Machine  Gearing. . .  .8vo,  2  oo 

Juptner,  H.  F.  V.     Siderology:  The  Science  of  Iron 8vo,  *s  oo 

Kansas  City  Bridge 4*o»  6  oo 

Kapp,  G.     Alternate  Current  Machinery.     (Science  Series  No.  96.) .  i6mo,  o  50 

Electric  Transmission  of  Energy I2mo,  3  50 

Keim,  A.  W.     Prevention  of  Dampness  in  Buildings 8vo,  *2  oo 

Keller,  S.  S.     Mathematics  for  Engineering  Students.     i2mo,  half  leather. 

Algebra  and  Trigonometry,  with  a  Chapter  on  Vectors *i  75 

Special  Algebra  Edition *i  oo 

Plane  and  Solid  Geometry *i  25 

Analytical  Geometry  and  Calculus *2  oo 

Kelsey,  W.  R.     Continuous-current  Dynamos  and  Motors 8vo,  *2  50 

Kemble,  W.  T.,  and  Underbill,  C.  R.     The  Periodic  Law  and  the  Hydrogen 

Spectrum 8vo,  paper,  *o  50 

Kemp,  J.  F.    Handbook  of  Rocks 8vo,  *i  50 

Kendall,  E.    Twelve  Figure  Cipher  Code 4to,  *I2  50 

Kennedy,  A.  B.  W.,  and  Thurston,  R.  H.     Kinematics  of  Machinery. 

(Science  Series  No.  54.) i6mo,  o  50 

Kennedy,  A.  B.  W.,  Unwin,  W.  C.,  and  Idell,  F.  E.     Compressed  Air. 

(Science  Series  No.  106.) i6mo,  o  50 

Kennedy,  R.     Modern  Engines  and  Power  Generators.     Six  Volumes.   4to,  15  oo 

Single  Volumes each,  3  oo 

Electrical  Installations.     Five  Volumes 4to,  15  oo 

Single  Volumes each,  3  50 

Flying  Machines;  Practice  and  Design i2mo,  *2  oo 

Principles  of  Aeroplane  Construction ^ 8vo,  *i  50 

Kennelly,  A.  E.     Electro-dynamic  Machinery 8vo,  I  50 

Kent,  W.    Strength  of  Materials.     (Science  Series  No.  41.) i6mo,  o  50 

Kershaw,  J.  B.  C.     Fuel,  Water  and  Gas  Analysis 8vo,  *2  50 

Electrometallurgy.     (Westminster  Series.) 8vo,  *2  oo 

The  Electric  Furnace  in  Iron  and  Steel  Production i2mo,  *i  50 

Kinzbrunner,  C.     Alternate  Current  Windings 8vo,  *i  50 

Continuous  Current  Armatures 8vo,  *i  50 

Testing  of  Alternating  Current  Machines 8vo,  *2  oo 

Kirkaldy,  W.  G.     David  Kirkaldy's  System  of  Mechanical  Testing 4to,  10  oo 

Kirkbride,  J.     Engraving  for  Illustration 8vo,  *i  50 

Kirkwood,  J.  P.     Filtration  of  River  Waters 4to,  7  50 

Klein,  J.  F.     Design  of  a  High-speed  Steam-engine 8vo,  *5  oo 

Physical  Significance  of  Entropy 8vo,  *i  50 

Kleinhans,  F.  B.     Boiler  Construction 8vo,  3  oo 

Knight,  R.-Adm.  A.  M.    Modern  Seamanship 8vo,  *7  50 

Half  morocco *g  oo 

Knox,  J.    Physico-Chemical  Calculations 12 mo,  *i  oo 

Knox,  W.  F.     Logarithm  Tables (In  Preparation.) 

Knott,  C.  G.,  and  Mackay,  J.  S.     Practical  Mathematics 8vo,  2  oo 

Koester,  F.     Steam-Electric  Power  Plants 4to,  *5  oo 

Hydroelectric  Developments  and  Engineering 4to,  *5  oo 

Koller,  T.    The  Utilization  of  Waste  Products 8vo,  *3  50 

Cosmetics 8vo,  *2  50 


16     D.  VAN  NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG 

Kirschke,  A.    Gas  and  Oil  Engines Z2mo,  *i  25 

Kretchmar,  K.     Yarn  and  Warp  Sizing 8vo,  *4  oo 

Lambert,  T.     Lead  and  its  Compounds 8vo,  *3  50 

Bone  Products  and  Manures 8vo,  *3  oo 

Lamborn,  L.  L.     Cottonseed  Products 8vo,  *3  oo 

Modern  Soaps,  Candles,  and  Glycerin 8vo,  *7  50 

Lamprecht,  R.     Recovery  Work  After  Pit  Fires.     Trans,  by  C.  Salter . .  8vo,  *4  oo 
Lanchester,  F.  W.     Aerial  Flight.    Two  Volumes.     8vo. 

Vol.   I.     Aerodynamics *6  oo 

Aerial  Flight.     Vol.  II.     Aerodonetics *6  oo 

Larner,  E.  T.     Principles  of  Alternating  Currents I2mo,  *i  25 

Larrabee,  C.  S.     Cipher  and  Secret  Letter  and  Telegraphic  Code i6mo,  o  60 

La  Rue,  B.  F.    Swing  Bridges.     (Science  Series  No.  107.) i6mo,  o  50 

Lassar-Cohn,  Dr.     Modern  Scientific  Chemistry.     Trans,  by  M.  M.  Patti- 

son  Muir i2mo,  *2  oo 

Latimer,  L.  H.,  Field,  C.  J.,  and  Howell,  J.  W.    Incandescent  Electric 

Lighting.     (Science  Series  No.  57.) i6mo,  o  50 

Latta,  M.  N.     Handbook  of  American  Gas-Engineering  Practice 8vo,  *4  50 

American  Producer  Gas  Practice, 4to,  *6  oo 

Leask,  A.  R.    Breakdowns  at  Sea i2mo,  2  oo 

Refrigerating  Machinery i2mo,  2  oo 

Lecky,  S.  T.  S.     "  Wrinkles  "  in  Practical  Navigation 8vo,  *8  oo 

Le  Doux,  M.     Ice-Making  Machines.     (Science  Series  No.  46.) ....  i6mo,  o  50 

Leeds,  C.  C.    Mechanical  Drawing  foi  Trade  Schools oblong  4to, 

High  School  Edition *i  25 

Machinery  Trades  Edition *2  oo 

Lefe"vre,  L.     Architectural  Pottery.     Trans,  by  H.  K.  Bird  and  W.  M. 

Binns 4to,  *7  50 

Lehner,  S.    Ink  Manufacture.     Trans,  by  A.  Morris  and  H.  Robson  . .  8vo,  *2  50 

Lemstrom,  S.     Electricity  in  Agriculture  and  Horticulture 8vo,  *i  50 

Le  Van,  W.  B.     Steam-Engine  Indicator.     (Science  Series  No.  78.) .  i6mo,  o  50 

Lewes,  V.  B.     Liquid  and  Gaseous  Fuels.     (Westminster  Series.). ..  .8vo,  *2  oo 

Lewis,  L.  P.    Railway  Signal  Engineering 8vo,  *3  50 

Lieber,  B.  F.     Lieber's  Standard  Telegraphic  Code 8vo,  *io  oo 

Code.     German  Edition 8vo,  *io  oo 

Spanish  Edition 8vo,  *io  oo 

French  Edition 8vo,  *io  oo 

Terminal  Index 8vo,  *2  50 

Lieber's  Appendix folio,  *is  oo 

Handy  Tables 4to,  *2  50 

Bankers  and  Stockbrokers'  Code  and  Merchants  and  Shippers'  Blank 

Tables 8vo,  *is  oo 

100,000,000  Combination  Code 8vo,  *io  oo 

Engineering  Code 8vo,  *i2  50 

Livermore,  V.  P.,  and  Williams,  J.     How  to  Become  a  Competent  Motor- 
man I2mo,  *i  oo 

Livingstone,  R.     Design  and  Construction  of  Commutators 8vo,  *2  25 

Lobben,  P.     Machinists'  and  Draftsmen's  Handbook 8vo,  2  50 

Locke,  A.  G.  and  C.  G.     Manufacture  of  Sulphuric  Acid 8vo,  10  oo 

Lockwood,  T.  D.    Electricity,  Magnetism,  and  Electro-telegraph 8vo,  2  50 


D.  VAN  NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG      17 

Lockwood,  T.  D.    Electrical  Measurement  and  the  Galvanometer .  i2mo,  o  75 

Lodge,  0.  J.     Elementary  Mechanics I2mo,  i  50 

Signalling  Across  Space  without  Wires 8vo,  *2  oo 

Loewenstein,  L.  C.,  and  Crissey,  C.  P.     Centrifugal  Pumps *4  So 

Lord,  R.  T.     Decorative  and  Fancy  Fabrics 8vo,  *3  50 

Loring,  A.  E.     A  Handbook  of  the  Electromagnetic  Telegraph i6mo,  o  50 

Handbook.     (Science  Series  No.  39.) i6mo,  o  50 

Low,  D.  A.    Applied  Mechanics  (Elementary) i6mo,  o  80 

Lubschez,  B.  J.    Perspective i2mo,  *i   50 

Lucke,  C.  E.     Gas  Engine  Design 8vo,  *3  oo 

Power  Plants:  Design,  Efficiency,  and  Power  Costs.     2  vols. 

(In  Preparation.) 

Lunge,  G.     Coal-tar  and  Ammonia.     Two  Volumes .8vo,  *i$  oo 

Manufacture  of  Sulphuric  Acid  and  Alkali.     Four  Volumes 8vo, 

Vol.     I.     Sulphuric  Acid.     In  two  parts *i5  oo 

Vol.   II.     Salt  Cake,  Hydrochloric  Acid  and  Leblanc  Soda.  In  two  parts  *i5  oo 

Vol.  III.     Ammonia  Soda. *io  oo 

Vol.  IV.  Electrolytic  Methods (In  Press.) 

Technical  Chemists'  Handbook i2mo,  leather,  *3  50 

Technical  Methods  of  Chemical  Analysis.     Trans,  by  C.  A.  Eeane. 

in  collaboration  with  the  corps  of  specialists. 

Vol.   I.     In  two  parts 8vo,  *i5  oo 

Vol.  n.    In  two  parts 8vo,  *i8  oo 

Vol.  m (In  Preparation.) 

Lupton,  A.,  Parr,  G.  D.  A.,  and  Perkin,  H.     Electricity  as  Applied  to 

Mining 8vo,  *4  50 

Luquer  L.  M.     Minerals  in  Rock  Sections 8vo,  *i  50 

Macewen,  H.  A.     Food  Inspection 8vo,  *2  50 

Mackenzie,  N.  F.     Notes  on  Irrigation  Works 8vo,  *2  50 

Mackie,  J.     How  to  Make  a  Woolen  Mill  Pay 8vo,  *2  oo 

Mackrow,  C.     Naval  Architect's  and  Shipbuilder's  Pocket-book. 

i6mo,  leather,  5  oo 

Maguire,  Wm.  R.     Domestic  Sanitary  Drainage  and  Plumbing 8vo,  4  oo 

Mallet,  A.     Compound  Engines.     Trans,  by  R.  R.  Buel.     (Science  Series 

No.  10.) i6mo, 

Mansfield,  A.  N.    Electro-magnets.     (Science  Series  No.  64.) i6mo,  o  50 

Marks,  E.  C.  R.     Construction  of  Cranes  and  Lifting  Machinery. . . .  i2mo,  *i  50 

Construction  and  Working  of  Pumps I2mo,  *i  50 

Manufacture  of  Iron  and  Steel  Tubes I2mo,  *2  oo 

Mechanical  Engineering  Materials I2mo,  *i  oo 

Marks,  G.  C.     Hydraulic  Power  Engineering 8vo,  3  50 

Inventions,  Patents  and  Designs I2mo,  *i  oo 

Marlow,  T.  G.     Drying  Machinery  and  Practice 8vo,  *5  oo 

Marsh,  C.  F.     Concise  Treatise  on  Reinforced  Concrete 8vo,  *2  50 

Reinforced  Concrete  Compression  Member  Diagram.    Mounted  on 

Cloth  Boards *i  50 

Marsh,  C.  F.,  and  Dunn,  W.     Manual  of  Reinforced  Concrete  and  Con- 
crete Block  Construction i6mo,  morocco,  *2  50 


18     D.  VAN  NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG 

Marshall,  W.  J.,  and  Sankey,  H.  R.     Gas  Engines.     (Westminster  Series.) 

8vo,  *2  oo 

Martin.  G,    Triumphs  and  Wonders  of  Modern  Chemistry 8vo,  *2  oo 

Martin,  N.    Properties  and  Design  of  Reinforced  Concrete i2mo,  *2  50 

Massie,  W.  W.,  and  Underbill,  C.  R.     Wireless  Telegraphy  and  Telephony. 

12010,  *i  oo 
Matheson,  D.     Australian  Saw-Miller's  Log  and  Timber  Ready  Reckoner. 

I2mo,  leather,  i  50 

Mathot,  R.  E.     Internal  Combustion  Engines 8vo,  *6  oo 

Maurice,  W.     Electric  Blasting  Apparatus  and  Explosives 8vo,  *3  50 

Shot  Firer's  Guide 8vo,  *i  50 

Maxwell,  J.  C.     Matter  and  Motion.     (Science  Series  No.  36.) i6mo,  o  50 

Maxwell,  W.  H.,  and  Brown,  J.  T.     Encyclopedia  of  Municipal  and  Sani- 
tary Engineering 4to,  *io  oo 

Mayer,  A.  M.     Lecture  Notes  on  Physics 8vo,  2  oo 

McCullough,  R.  S.     Mechanical  Theory  of  Heat 8vo,  3  50 

Mclntosh,  J.  G.     Technology  of  Sugar 8vo,  *4  50 

Industrial  Alcohol 8vo,  *3  oo 

Manufacture  of  Varnishes  and  Kindred  Industries.     Three  Volumes. 

8vo. 

Vol.     I.     Oil  Crushing,  Refining  and  Boiling *3  50 

Vol.   II.     Varnish  Materials  and  Oil  Varnish  Making *4  oo 

Vol.  HI.    Spirit  Varnishes  and  Materials *4  So 

McKnight,  J.  D.,  and  Brown,  A.  W.     Marine  Multitubular  Boilers *i  50 

McMaster,  J.  B.    Bridge  and  Tunnel  Centres.     (Science  Series  No.  20.) 

i6mo,  o  50 

McMechen,  F.  L.      Tests  for  Ores,  Minerals  and  Metals i2mo,  *i  oo 

McNeill,  B.     McNeill's  Code 8vo,  *6  oo 

McPherson,  J.  A.    Water- works  Distribution. .. 8vo,  2  50 

Melick,  C.  W.     Dairy  Laboratory  Guide i2mo,  *i  25 

Merck,  E.    Chemical  Reagents;  Their  Purity  and  Tests 8vo,  *i  50 

Merritt,  Wm.  H.     Field  Testing  for  Gold  and  Silver i6mo,  leather,  i  50 

Messer,  W.  A.    Railway  Permanent  Way 8vo,  (In  Press.) 

Meyer,  J.  G.  A.,  and  Pecker,  C.  G.     Mechanical  Drawing  and  Machine 

Design 4to,  5  oo 

Michell,  S.     Mine  Drainage 8vo,  10  oo 

Mierzinski,  S.     Waterproofing  of  Fabrics.     Trans,  by  A.  Morris  and  H. 

Robson 8vo,  *2  50 

Miller,  E.  H.     Quantitative  Analysis  for  Mining  Engineers 8vo,  *i  50 

Miller,  G.  A.    Determinants.     (Science  Series  No.  105.) i6mo, 

Milroy,  M.  E.  W.     Home  Lace-making i2mo,  *i  oo 

Minifie,  W.     Mechanical  Drawing 8vo,  *4  oo 

Mitchell,  C.  F.,  and  G.  A.    Building  Construction  and  Drawing. . .  i2mo, 

Elementary  Course *i  50 

Advanced  Course *2  50 

Mitchell,  C.  A.,  and  Prideaux,  R.  M.     Fibres  Used  in  Textile  and  Allied 

Industries : 8vo,  *3  oo 

Modern  Meteorology i2mo,  i  50 

Monckton,  C.  C.  F.     Radiotelegraphy.     (Westminster  Series.) 8vo,  *2  oo 

Monteverde,  R.  D.     Vest  Pocket  Glossary  of  English-Spanish,  Spanish- 
English  Technical  Terms 64mo,  leather,  *i  oo 


D.   VAN  NOSTRAND   COMPANY'S   SHORT  TITLE  CATALOG  19 

Moore,  E.  C.  S.     New  Tables  for  the  Complete  Solution  of  Ganguillet  and 

Kutter's  Formula 8vo,  *5  oo 

Morecroft,  J.  H.,  and  Hehre,  F.  W.     Short  Course  in  Electrical  Testing. 

8vo,  *i  50 

More  ing,  C.  A.,  and  Neal,  T.    New  General  and  Mining  Telegraph  Code,  8vo,  *5  oo 

Morgan,  A.  P.     Wireless  Telegraph  Apparatus  for  Amateurs ; .  i2mo,  *i  50 

Moses,  A.  J.     The  Characters  of  Crystals „ . 8vo,  *2  oo 

Moses,  A.  J.,  and  Parsons,  C.  L.    Elements  of  Mineralogy 8vo,  *2  50 

Moss,  S.  A.  Elements  of  Gas  Engine  Design.  (Science  Series  No.i2i.)i6mo,  o  50 

The  Lay-out  of  Corliss  Valve  Gears.   (Science  Series  No.  119.).  i6mo,  o  50 

Mulford,  A.  C.    Boundaries  and  Landmarks t i2mo,  *i  oo 

Mullin,  J.  P.     Modern  Moulding  and  Pattern-making I2mo,  2  50 

Munby,  A.  E.    Chemistry  and  Physics  of  Building  Materials.     (Westmin- 
ster Series.) .,.  „ 8vo,  *2  oo 

Murphy,  J.  G.     Practical  Mining i6mo,  i  oo 

Murray,  J.  A.     Soils  and  Manures.     (Westminster  Series.) .'. 8vo,  *2  oo 

Naquet,  A.     Legal  Chemistry , . .  I2mo,  2  oo 

Nasmith,  J.     The  Student's  Cotton  Spinning 8vo,  3  oo 

Recent  Cotton  Mill  Construction .-. I2mo,  2  oo 

Neave,  G.  B.,  and  Heilbron,  I.  M.    Identification  of  Organic  Compounds. 

i2mo,  *i  25 

Neilson,  R.  M.     Aeroplane  Patents 8vo,  *2  oo 

Nerz,  F.     Searchlights.     Trans,  by  C.  Rodgers '. 8vo,  *3  oo 

Nesbit,  A.  F.    Electricity  and  Magnetism (In  Preparation.) 

Neuberger,  H.,  and  Noalhat,  H.     Technology  of  Petroleum.     Trans,  by  J. 

G.  Mclntosh 8vo,  *io  oo 

Newall,  J.  W.     Drawing,  Sizing  and  Cutting  Bevel-gears 8vo,  i  50 

Nicol,  G.     Ship  Construction' and  Calculations 8vo,  *4  50 

Nipher,  F.  E.     Theory  of  Magnetic  Measurements i2mo,  i  oo 

Nisbet,  H.     Grammar  of  Textile  Design , , 8vo,  *3  oo 

Nolan,  H.    The  Telescope.     (Science  Series  No,  51.) i6mo,  o  50 

Noll,  A.     How  to  Wire  Buildings I2mo,  i  50 

North,  H.  B.    Laboratory  Notes  of  Experiments  in  General  Chemistry. 

(In  Press.) 

Nugent,  E.     Treatise  on  Optics i2mo,  i  50 

O'Connor,  H.  The  Gas  Engineer's  Pocketbook. i2mo,  leather,  3  50 

Petrol  Air  Gas i2mo,  *o  75 

Ohm,  G.  S.,  and  Lockwood,  T.  D.  Galvanic  Circuit.  Translated  by 

William  Francis.  (Science  Series  No.  102.) i6mo,  o  50 

Olsen,  J.  C.  Text-book  of  Quantitative  Chemical  Analysis 8vo,  *4  oo 

Olsson,  A.  Motor  Control,  in  Turret  Turning  and  Gun  Elevating.  (U.  S. 

Navy  Electrical  Series,  No.  i.) i2mo,  paper,  *o  50 

Oudin,  M.  A.  Standard  Polyphase  Apparatus  and  Systems 8vo,  *3  oo 

Pakes,  W.  C.  C.,  and  Nankivell,  A.  T.    The  Science  of  Hygiene.  -8vo,  *i  75 

Palaz,  A.     Industrial  Photometry.     Trans,  by  G.  W.  Patterson,  Jr. . .  8vo,  *4  oo 

Pamely,  C.     Colliery  Manager's  Handbook 8vo,  *io  oo 

Parr,  G.  D.  A.     Electrical  Engineering  Measuring  Instruments 8vo,  *3  50 

Parry.  E.  J.     Chemistry  of  Essential  Oils  and  Artificial  Perfumes 8vo,  *s  oo 


20      D.  VAN   NOSTRAND   COMPANY'S  SHORT  TITLE  CATALOG 

Parry,  E.  J.    Foods  and  Drugs.    Two  Volun?es 8vo, 

Vol.   I.    Chemical  and  Microscopical  Analysis  of  Foods  and  Drugs.  *7  50 

Vol.  II.    Sale  of  Food  and  Drugs  Act *3  oo 

Parry,  E.  J.,  and  Coste,  J.  H.     Chemistry  of  Pigments 8vo,  *4  50 

Parry,  L.  A.     Risk  and  Dangers  of  Various  Occupations 8vo,  *3  oo 

Parshall,  H.  F.,  and  Hobart,  H.  M.     Armature  Windings 4to,  *7  50 

Electric  Railway  Engineering 4to,  *io  oo 

Parshall,  H.  F.,  and  Parry,  E.     Electrical  Equipment  of  Tramways (In  Press.) 

Parsons,  S.  J.     Malleable  Cast  Iron 8vo,  *2  50 

Partington,  J.  R.    Higher  Mathematics  for  Chemical  Students.  .i2mo,  *2  oo 

Passmore,  A.  C.     Technical  Terms  Used  in  Architecture 8vo,  *3  50 

Paterson,  G.  W.  L.    Wiring  Calculations i2mo,  *2  oo 

Patterson,  D.     The  Color  Printing  of  Carpet  Yarns. . .  „ 8vo,  *3  50 

Color  Matching  on  Textiles 8vo,  *3  oo 

The  Science  of  Color  Mixing 8vo,  *3  oo 

Paulding,  C.  P.     Condensation  of  Steam  in  Covered  and  Bare  Pipes    8vo,  *2  oo 

Transmission  of  Heat  through  Cold-storage  Insulation i2mo,  *i  oo 

Payne,  D.  W.    Iron  Founders*  Handbook (In  Press.) 

Peddie,  R.  A.    Engineering  and  Metallurgical  Books i2mo,  *i  50 

Peirce,  B.     System  of  Analytic  Mechanics 4to,  10  oo 

Pendred,  V.     The  Railway  Locomotive.     (Westminster  Series.) 8vo,  *2  oo 

Perkin,  F.  M.     Practical  Methods  of  Inorganic  Chemistry i2mo,  *i  oo 

Perrigo,  O.  E.     Change  Gear  Devices 8vo,  i  oo 

Perrine,  F.  A.  C.     Conductors  for  Electrical  Distribution 8vo,  *3  50 

Perry,  J.     Applied  Mechanics 8vo,  *2  50 

Petit,  G.     White  Lead  and  Zinc  White  Paints 8vo,  *i  50 

Petit,  R.    How  to  Build  an  Aeroplane.     Trans,  by  T.  O'B.  Hubbard,  and 

J.  H.  Ledeboer 8vo,  *i  50 

Pettit,  Lieut.  J.  S.     Graphic  Processes.     (Science  Series  No.  76.) . . .  i6mo,  o  50 
Philbrick,  P.  H.    Beams  and  Girders.     (Science  Series  No.  C8.) . . .  i6mo, 

Phillips,  J.    Engineering  Chemistry 8vo,  *4  50 

Gold  Assaying 8vo,  *2  50 

Dangerous  Goods 8vo,  3  50 

Phin,  J.    Seven  Follies  of  Science i2mo,  *i  25 

Pickworth,  C.  N.    The  Indicator  Handbook.     Two  Volumes.  .12010,  each,  150 

Logarithms  for  Beginners I2mo,  boards,  o  50 

The  Slide  Rule i2mo,  i  oo 

Plattner's  Manual  of  Blow-pipe  Analysis.    Eighth  Edition,  revised.    Trans. 

by  H.  B.  Cornwall 8vo,  *4  oo 

Plympton,  G.  W.   The  Aneroid  Barometer.    (Science  Series  No.  35.)   i6mo,  o  50 

How  to  become  an  Engineer.      (Science  Series  No.  100.) i6mo,  o  50 

Van  Nostrand's  Table  Book.     (Science  Series  No.  104.) i6mo,  o  50 

Pochet,  M.  L.     Steam  Injectors.     Translated  from  the  French.     (Science 

Series  No.  2g.) i6mo,  o  50 

Pocket  Logarithms  to  Four  Places.     (Science  Series  No.  65.) i6mo,  o  50 

leather,  i  oo 

Polleyn,  F.     Dressings  and  Finishings  for  Textile  Fabrics 8vo,  *3  oo 

Pope,  F.  L.     Modern  Practice  of  the  Electric  Telegraph 8vo,  i  50 

Popplewell,  W.  C.  Elemsntary  Treatise  on  Heat  and  Heat  Engines.  .  i2mo,  *3  oo 

Prevention  of  Smoke 8vo,  *3  50 

Strength  of  Materials 8vo,  *i  75 


D.  VAN   NOSTRAND   COMPANY'S  SHORT  TITLE   CATALOG     21 

Porter,  J.  R.    Helicopter  Flying  Machine i2mo,  *i  25 

Potter,  T.     Concrete 8vo,  *3  oo 

Potts,  H.  E.    Chemistry  of  the  Rubber  Industry.     (Outlines  of  Indus- 
trial Chemistry) 8vo,  *2  oo 

Practical  Compounding  of  Oils,  Tallow  and  Grease 8vo,  *3  50 

Practical  Iron  Founding i2mo,  i  50 

Pratt,  K.    Boiler  Draught i2mo,  *i  25 

Pray,  T.,  Jr.     Twenty  Years  with  the  Indicator 8vo,  2  50 

Steam  Tables  and  Engine  Constant 8vo,  2  oo 

Calorimeter  Tables 8vo,  i  oo 

Preece,  W.  H.     Electric  Lamps (In  Press.) 

Prelini,  C.     Earth  and  Rock  Excavation 8vo,  *3  oo 

Graphical  Determination  of  Earth  Slopes 8vo,  *2  oo 

Tunneling.    New  Edition 8vo,  *3  oo 

Dredging.    A  Practical  Treatise 8vo,  *3  oo 

Prescott,  A.  B.     Organic  Analysis 8vo,  5  oo 

Prescott,  A.  B.,  and  Johnson,  O.  C.     Qualitative  Chemical  Analysis.  .  .8vo,  *3  50 
Prescott,  A.  B.,  and  Sullivan,  E.  C.     First  Book  in  Qualitative  Chemistry. 

i2mo,  *i  50 

Prideaux,  E.  B.  R.    Problems  in  Physical  Chemistry 8vo,  *2  oo 

Pritchard,  O.  G.     The  Manufacture  of  Electric-light  Carbons .  .  8vo,  paper,  *o  60 
Pullen,  W.  W.  F.     Application  of  Graphic  Methods  to  the  Design  of 

Structures i2mo,  *2  50 

Injectors:  Theory,  Construction  and  Working i2mo,  *i  50 

Pulsifer,  W.  H.     Notes  for  a  History  of  Lead 8vo,  4  oo 

Purchase,  W.  R.     Masonry i2mo,  *3  oo 

Putsch,  A.     Gas  and  Coal-dust  Firing 8vo,  *3  oo 

Pynchon,  T.  R.     Introduction  to  Chemical  Physics 8vo,  3  oo 

Rafter  G.  W.     Mechanics  of  Ventilation.     (Science  Series  No.  33.) .  i6mo,  o  50 

—  Potable  Water,     (Science  Series  No.  103.) i6mc  50 

-Treatment  of  Septic  Sewage.     (Science  Series  No.  118.). .  . .  i6mo  50 

Rafter,  G.  W.,  and  Baker,  M.  N.     Sewage  Disposal  in  the  United  States. 

4to,  *6  oo 

Raikes,  H.  P.     Sewage  Disposal  Works 8vo,  *4  oo 

Railway  Shop  Up-to-Date 4to,  2  oo 

Ramp,  H.  M.     Foundry  Practice (In  Press.) 

Randall,  P.  M.     Quartz  Operator's  Handbook I2mo,  2  oo 

Randau,  P.     Enamels  and  Enamelling 8vo,  *4  oo 

Rankine,  W.  J.  M.     Applied  Mechanics 8vo,  5  oo 

Civil  Engineering . .. 8vo,  6  50 

Machinery  and  Millwork     . . , 8vo,  5  oo 

The  Steam-engine  and  Other  Prime  Movers 8vo,  5  oo 

Useful  Rules  and  Tables 8vo,  4  oo 

Rankine,  W.  J.  M.,  and  Bamber,  E.  F.     A  Mechanical  Text-book 8vo,  3  50 

Raphael,  F.  C.     Localization  of  Faults  in  Electric  Light  and  Power  Mains. 

8vo,  *3  oo 
Rasch,  E.    Electric  Arc  Phenomena.    Trans,  by  K.  Tornberg  .(In  Press.) 

Rathbone,  R.  L.  B.     Simple  Jewellery 8vo,  *2  oo 

Rateau,  A.     Flow  of  Steam  through  Nozzles  and  Orifices.     Trans,  by  H. 

Bo  Brydon 8vo,  *i  50 


22      D.  VAN   NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG 

Rausenberger,  F.     The  Theory  of  the  Recoil  of  Guns 8vo,  *4  50 

Rautenstrauch,  W.    Notes  on  the  Elements  of  Machine  Design. 8 vo,  boards,  *i  50 
Rautenstrauch,  W.,  and  Williams,  J.  T.     Machine  Drafting  and  Empirical 
Design. 

Part   I.  Machine  Drafting 8vo,  *i  25 

Part  II.  Empirical  Design (In  Preparation.) 

Raymond,  E.  B.     Alternating  Current  Engineering i2mo,  *2  50 

Rayner,  H.     Silk  Throwing  and  Waste  Silk  Spinning 8vo,  *2  50 

Recipes  for  the  Color,  Paint,  Varnish,  Oil,  Soap  and  Drysaltery  Trades .  8vo,  *3  50 

Recipes  for  Flint  Glass  Making I2mo,  *4  50 

Redfera,  J.  B.    Bells,  Telephones  (Installation  Manuals  Series)  i6mo, 

(In  Press.) 

Redwood,  B.     Petroleum.     (Science  Series  No.  92.) i6mo,  o  50 

Reed's  Engineers'  Handbook 8vo,  *s  oo 

Key  to  the  Nineteenth  Edition  of  Reed's  Engineers'  Handbook . .  8vo,  *3  oo 

Useful  Hints  to  Sea-going  Engineers I2mo,  i  50 

Marine  Boilers I2mo,  2  oo 

—  Guide  to  the  Use  of  the  Slide  Valve i2mo,  *i  60 

Reinhardt,  C.  W.     Lettering  for  Draftsmen,  Engineers,  and  Students. 

oblong  410,  boards,  I  oo 

The  Technic  of  Mechanical  Drafting oblong  4to,  boards,  *i  oo 

Reiser,  F.     Hardening  and  Tempering  of  Steel.     Trans,  by  A.  Morris  and 

H.  Robson i2mo,  *2  50 

Reiser,  N.     Faults  in  the  Manufacture  of  Woolen  Goods.     Trans,  by  A. 

Morris  and  H.  Robson 8vo,  *2  50 

Spinning  and  Weaving  Calculations 8vo,  *5  oo 

Renwick,  W.  G.     Marble  and  Marble  Working 8vo,  5  oo 

Reynolds,   0.,  and  Idell,   F.   E.     Triple  Expansion  Engines.     (Science 

Series  No.  99.) i6mop  o  5° 

Rhead,  G.  F.     Simple  Structural  Woodwork 12 mo,  *i  oo 

Rice,  J.  M.,  and  Johnson,  W.  W.     A  New  Method  of  Obtaining  the  Differ- 
ential of  Functions i2mo,  o  50 

Richards,  W.  A.,  and  North,  H.  B.    Manual  of  Cement  Testing i2mo,  *i  50 

Richardson,  J.     The  Modern  Steam  Engine 8vo,  *3  50 

Richardson,  S.  S.     Magnetism  and  Electricity I2mo,  *2  oo 

Rideal,  S.     Glue  and  Glue  Testing 8vo,  *4  oo 

Rimmer,  E.  J.    Boiler  Explosions,  Collapses  and  Mishaps 8vo,  *i  75 

Rings,  F.     Concrete  in  Theory  and  Practice i2mo,  *2  50 

Ripper,  W.     Course  of  Instruction  in  Machine  Drawing folio,  *6  oo 

Roberts,  F.  C.     Figure  of  the  Earth.     (Science  Series  No.  79.) i6mo,  o  50 

Roberts,  J.,  Jr.     Laboratory  Work  in  Electrical  Engineering 8vo,  *2  oo 

Robertson,  L.  S.     Water-tube  Boilers 8vo,  2  oo 

Robinson,  J.  B.     Architectural  Composition 8vo,  *2  50 

Robinson,  S.  W.     Practical  Treatise  on  the  Teeth  of  Wheels.     (Science 

Series  No.  24.) i6mo,  o  50 

Railroad  Economics.     (Science  Series  No.  59.) i6mo,  o  50 

Wrought  Iron  Bridge  Members.     (Science  Series  No.  60.) i6mo,  o  50 

Robson,  J.  H.    Machine  Drawing  and  Sketching 8vo,  *i  50 

Boebling,  J  A.     Long  and  Short  Span  Railway  Bridges folio,  25  oo 

Rogers,  A.     A  Laboratory  Guide  of  Industrial  Chemistry I2mo,  *i  50 

Rogers,  A.,  and  Aubert,  A.  B.     Industrial  Chemistry 8vo,  *s  oo 


D.  VAN   NOSTRAND   COMPANY'S   SHORT   TITLE  CATALOG     23 

Rogers,  F.    Magnetism  of  Iron  Vessels.     (Science  Series  No.  30.) . .  i6mo,  o  50 
Rohland,  P.     Colloidal  and  Cyrstalloidal   State  of  Matter.     Trans,  by 

W.  J.  Britland  and  H.  E.  Potts ,.-.. i2mo,  *i  25 

Rollins,  W.    Notes  on  X-Light 8vo,  *$  oo 

Rollinson,  C.    Alphabets Oblong,  i2mo,  *i  oo 

Rose,  J.     The  Pattern-makers'  Assistant 8vo,  2  50 

Key  to  Engines  and  Engine-running I2mo,  2  50 

Rose,  T.  K.     The  Precious  Metals.     (Westminster  Series.) 8vo,  *2  oo 

Rosenhain,  W.     Glass  Manufacture.     (Westminster  Series.) 8vo,  *2  oo 

Ross,  W.  A.     Plowpipe  in  Chemistry  and  Metallurgy 12 mo,  *2  oo 

Rossiter,  J.  T.     Steam  Engines.     (Westminster  Series.) 8vo  (In  Press.) 

Pumps  and  Pumping  Machinery.     (Westminster  Series.) 8vo, 

(In  Press.) 

Roth.    Physical  Chemistry 8vo,  *2  oo 

Rouillion,  L.     The  Economics  of  Manual  Training 8vo,  2  oo 

Rowan,  F.  J.    Practical  Physics  of  the  Modern  Steam-boiler 8vo,  *3  oo 

Rowan,   F.   J.,   and  Idell,   F.   E.     Boiler  Incrustation  and   Corrosion. 

(Science  Series  No.  27.) i6mo,  o  50 

Roxburgh,  W.     Genera!  Foundry  Practice 8vo,  *3  50 

Ruhmer,  E.     Wireless  Telephony.     Trans,  by  J.  Erskine-Murray . .  .  .8vo,  *3  50 

Russell,  A.     Theory  of  Electric  Cables  and  Networks 8vo,  *3  oo 

Sabine,  R.     History  and  Progress  of  the  Electric  Telegraph i2mo,  i  25 

Saeltzer  A.     Treatise  on  Acoustics i2mo,  i  oo 

Salomons,  D.     Electric  Light  Installations.     i2mo. 

Vol.    I.     The  Management  of  Accumulators 2  50 

Vol.  II.     Apparatus 2  25 

Vol.  III.     Applications i  50 

Sanford,  P.  G.     Nitro-explosives 8vo,  *4  oo 

Saunders,  C.  H.     Handbook  of  Practical  Mechanics i6mo,  i  oo 

leather,  i  25 

Saunnier,  C.     Watchmaker's  Handbook i2ino,  3  oo 

Sayers,  H.  M.     Brakes  for  Tram  Cars 8vo,  *i  25 

Scheele,  C.  W.     Chemical  Essays 8vo,  *2  oo 

Schellen,  H.     Magneto-electric  and  Dynamo-electric  Machines 8vo,  5  oo 

Scherer,  R.     Casein.     Trans,  by  C.  Salter 8vo,  *3  oo 

Schidrowitz,  P.    Rubber,  Its  Production  and  Industrial  Uses 8vo,  *$  oo 

Schindler,  K.     Iron  and  Steel  Construction  Works i2mo,  *i  25 

Schmall,  C.  N.     First  Course  in  Analytic  Geometry,  Plane  and  Solid. 

I2mo,  half  leather,  *i  75 

Schmall,  C.  N.,  and  Shack,  S.  M.     Elements  of  Plane  Geometry. . .  .  i2mo,  *i  25 

Schmeer,  L.     Flow  of  Water 8vo,  *3  oo 

Schumann,  F.     A  Manual  of  Heating  and  Ventilation i2mo,  leather,  i  50 

Schwarz,  E.  H.  L.     Causal  Geology 8vo,  *2  50 

Schweizer,  V.,  Distillation  of  Resins 8vo,  *3  50 

Scott,  W.  W.     Qualitative  Analysis.     A  Laboratory  Manual 8vo,  *i  50 

Scribner,  J.  M.     Engineers'  and  Mechanics'  Companion  . . .  i6mo,  leather,  i  50 

Searle,  A.  B.     Modern  Brickmaking 8vo,  *5  oo 

Searle,  G.  M.     "  Sumners'  Method."     Condensed  and  Improved.    (Science 

Series  No.  124.) i6mo,  o  50 

Seaton,  A.  E.     Manual  of  Marine  Engineering 8vo,  6  oo 


24     D.  VAN    NOSTRAND   COMPANY'S   SHORT  TITLE   CATALOG 

Seaton,  A.  E.,  and  Rounthwaite,  H.  M.     Pocket-book  of  Marine  Engineer- 
ing  i6mo,  leather,  3  oo 

Seeligmann,  T.,  Torrilhon,  G.  L.,  and  Falconnet,  H.     India  Rubber  and 

Gutta  Percha.     Trans,  by  J.  G.  Mclntosh 8vo,  *5  oo 

Seidell,  A.     Solubilities  of  Inorganic  and  Organic  Substances 8vo,  *3  oo 

SeUew,  W.  H.     Steel  Rails 4to  (In  Press.) 

Senter,  G.     Outlines  of  Physical  Chemistry i2mo,  *i  75 

Textbook  of  Inorganic  Chemistry i2mo,  *i  75 

Sever,  G.  F.     Electric  Engineering  Experiments 8vo,  boards,  *i  oo 

Sever,  G.  F.,  and  Townsend,  F.     Laboratory  and  Factory  Tests  in  Electrical, 

Engineering 8vo,  *2  50 

Sewall,  C.  H.     Wireless  Telegraphy 8vo,  *2  oo 

Lessons  in  Telegraphy I2mo,  *i  oo 

Sewell,  T.     Elements  of  Electrical  Engineering 8vo,  *3  oo 

The  Construction  of  Dynamos 8mo,  *3  oo 

Sexton,  A.  H.     Fuel  and  Refractory  Materials I2mo,  *2  50 

Chemistry  of  the  Materials  of  Engineering I2mo,  *2  50 

Alloys  (Non-Ferrous) 8vo,  *3  oo 

The  Metallurgy  of  Iron  and  Steel 8vo,  *6  50 

Seymour,  A.     Practical  Lithography 8vo,  *2  50 

Modern  Printing  Inks 8vo,  *2  oo 

Shaw,  Henry  S.  H.    Mechanical  Integrators.     (Science  Series  No.  83.) 

i6mo,  o  50 

Shaw,  P.  E.     Course  of  Practical  Magnetism  and  Electricity 8vo,  *i  oo 

Shaw,  S.     History  of  the  Staffordshire  Potteries 8vo,  *3  oo 

Chemistry  of  Compounds  Used  in  Porcelain  Manufacture 8vo,  *5  oo 

Shaw,  W.  N.    Forecasting  Weather 8vo,  *3  50 

Sheldon,  S.,  and  Hausmann,  E.    Direct  Current  Machines i2mo,  *2  50 

Alternating  Current  Machines i2mo,  *2  50 

Sheldon,  S.,  and  Hausmann,  E.     Electric  Traction  and  Transmission 

Engineering i2mo,  *2  50 

Sherriff,  F.  F.     Oil  Merchants'  Manual i2mo,  *3  50 

Shields,  J.  E.     Notes  on  Engineering  Construction I2mo,  i  50 

Shock,  W.  H.     Steam  Boilers 4to,  half  morocco,  15  oo 

Shreve,  S.  H.     Strength  of  Bridges  and  Roofs 8vo,  3  50 

Shunk,  W.  F.     The  Field  Engineer i2mo,  morocco,  2  50 

Simmons,  W.  H.,  and  Appleton,  H.  A.    Handbook  of  Soap  Manufacture. 

8vo,  *3  oo 

Simmons,  W.  H.,  and  Mitchell,  C.  A.     Edible  Fats  and  Oils 8vo,  *3  oo 

Simms,  F.  W.     The  Principles  and  Practice  of  Leveling 8vo,  2  50 

Practical  Tunneling 8vo,  7  50 

Simpson,  G.    The  Naval  Constructor i2mo,  morocco,  *5  oo 

Simpson,  W.    Foundations 8vo,   (In  Press.) 

Sinclair,  A.     Development  of  the  Locomotive  Engine  . . .  8vo,  half  leather,  5  oo 

Twentieth  Century  Locomotive 8vo,  half  leather,  *5  oo 

Sindall,  R.  W.,  and  Bacon,  W.  N.     The  Testing  of  Wood  Pulp 8vo, . .  *2  50 

Sindall,  R.  W.     Manufacture  of  Paper.     (Westminster  Series.) 8vo,  *2  oo 

Sloane,  T.  O'C.     Elementary  Electrical  Calculations i2mo,  *2  oo 

Smith,  C.  A.  M.     Handbook  of  Testing,  MATERIALS 8vo,  *2  50 

Smith,  C.  A.  M.,  and  Warren,  A.  G.    New  Steam  Tables 8vo, 

Smith,  C.  F.     Practical  Alternating  Currents  and  Testing 8vo,  *2  50 


D.  VAN    NOSTRAND   COMPANY'S   SHOKT  TITLE   CATALOG     25 

Smith,  C.  F.    Practical  Testing  of  Dynamos  and  Motors 8vo,  *a  oo 

Smith,  F.  E.     Handbook  of  General  Instruction  for  Mechanics.  .  . .  I2mo,  i  50 

Smith,  J.  C.     Manufacture  of  Paint 8vo,  *3  oo 

Smith,  R.  H.    Principles  of  Machine  Work i2mo,  *3  oo 

Elements  of  Machine  Work i2mo,  *2  oo 

Smith,  W.     Chemistry  of  Hat  Manufacturing i2mo,  *3  oo 

Snell,  A.  T.     Electric  Motive  Power 8vo,  *4  oo 

Snow,  W.  G.     Pocketbook  of  Steam  Heating  and  Ventilation.    (In  Press.) 
Snow,  W.  G.,  and  Nolan,  T.     Ventilation  of  Buildings.     (Science  Series 

No.  5.) i6mo,  o  50 

Soddy,  F.     Radioactivity 8vo,  *3  oo 

Solomon,  M.     Electric  Lamps.     (Westminster  Series.) 8vo,  *2  oo 

Sothern,  J.  W.     The  Marine  Steam  Turbine 8vo,  *s  oo 

Southcombe,  J.  E.    Paints,  Oils  and  Varnishes.     (Outlines  of  Indus- 
trial Chemistry.) 8vo,   (In  Press.) 

Soxhlet,  D.  H.     Dyeing  and  Staining  Marble.     Trans,  by  A.  Morris  and 

H.  Robson 8vo,  *2  50 

Spang,  H.  W.     A  Practical  Treatise  on  Lightning  Protection i2mo,  i  oo 

Spangenburg,    L.     Fatigue    of    Metals.     Translated   by    S.    H.    Shreve. 

(Science  Series  No.  23.) i6mo,  o  50 

Specht,  G.  J.,  Hardy,  A.  S.,  McMaster,  J.B  .,  and  Walling.     Topographical 

Surveying.     (Science  Series  No.  72.). i6mo,  o  50 

Speyers,  C.  L.     Text-book  of  Physical  Chemistry 8vo,  *2  25 

Stahl,  A.  W.     Transmission  of  Power.     (Science  Series  No.  28.) . . .  i6mo, 

Stahl,  A.  W.,  and  Woods,  A.  T.     Elementary  Mechanism I2mo,  *2  oo 

Staley,  C.,  and  Pierson,  G.  S.     The  Separate  System  of  Sewerage. . .  .8vo,  *3  oo 

Standage,  H.  C.     Leatherworkers'  Manual 8vo,  *3  50 

Sealing  Waxes,  Wafers,  and  Other  Adhesives 8vo,  *2  oo 

Agglutinants  of  all  Kinds  for  all  Purposes 12010,  *3  50 

Stansbie,  J.  H.     Iron  and  Steel.     (Westminster  Series.) 8vo,  *2  oo 

Steadman,  F.  M.     Unit  Photography  and  Actinometry (In  Press.) 

Steinman,  D.  B.     Suspension  Bridges  and  Cantilevers.     (Science  Series 

No.  127) o  50 

Stevens,  H.  P.     Paper  Mill  Chemist i6mo,  *2  50 

Stevenson,  J.  L.     Blast-Furnace  Calculations. I2mo,  leather,  *2  oo 

Stewart,  A.     Modern  Polyphase  Machinery i2mo,  *2  oo 

Stewart,  G.     Modern  Steam  Traps i2mo,  *i  25 

Stiles,  A.     Tables  for  Field  Engineers. I2mo,  i  oo 

Stillman,  P.     Steam-engine  Indicator I2mo,  i  oo 

Stodola,  A.     Steam  Turbines.     Trans,  by  L.  C.  Loewenstein 8vo,  *5  oo 

Stone,  H.     The  Timbers  of  Commerce 8vo,  3  50 

Stone,  Gen.  R.    New  Roads  and  Road  Laws , i2mo,  i  oo 

Stopes,  M.     Ancient  Plants 8vo,  *2  oo 

The  Study  of  Plant  Life 8vo,  *2  oo 

Stumpf,  Prof.     Una-Flow  of  Steam  Engine 4to,  *3  50 

Sudborough,  J.  J.,  and  James,  T.  C.     Practical  Organic  Chemistry.  .  I2mo,  *2  oo 

Suffling,  E.  R.     Treatise  on  the  Art  of  Glass  Painting 8vo,  *3  50 

Suggate,  A.     Elements  of  Engineering  Estimating i2mo, 

Swan,  K.     Patents,  Designs  and  Trade  Marks.      (Westminster  Series.). 

8vo,  *2  oo 

Sweet,  S.  H.     Special  Report  on  Coal 8vo,  3  oo 


26     D.  VAN   NOSTRAND   COMPANY'S   SHORT  TITLE  CATALOG 

Swinburne,  J.,  Wordingham,  C,  H.,  and  Martin,  T.  C.     Eletcric  Currents. 

(Science  Series  No.  109.) i6mo,  o  50 

Swoope,  C.  W.     Practical  Lessons  in  Electricity i2mo,  *2  oo 

Tailfer,  L.     Bleaching  Linen  and  Cotton  Yarn  and  Fabrics 8vo,  *s  oo 

Tate,  J.  S.     Surcharged  and  Different  Forms  of  Retaining- walls.     (Science 

Series  No.  7.) i6mo,  o  50 

Taylor,  E.  N.    Small  Water  Supplies i2mo,  *2  oo 

Templeton,  W.     Practical  Mechanic's  Workshop  Companion. 

i2mo,  morocco,  2  oo 
Terry,  H.  L.     India  Rubber  and  its  Manufacture.     (Westminster  Series.) 

8vo,  *2  oo 
Thayer,  H.  R.    Structural  Design.    8vo. 

Vol.     I.    Elements  of  Structural  Design *2  oo 

Vol.    II.    Design  of  Simple  Structures (In  Preparation.) 

Vol.  III.    Design  of  Advanced  Structures (In  Preparation.) 

Thiess,  J.  B.  and  Joy,  G.  A.    Toll  Telephone  Practice 8vo,  *3  50 

Thorn,  C.,  and  Jones,  W.  H.     Telegraphic  Connections oblong  i2mo,  i  50 

Thomas,  C.  W.     Paper-makers'  Handbook (In  Press.) 

Thompson,  A.  B.     Oil  Fields  of  Russia 4to,  *7  50 

Petroleum  Mining  and  Oil  Field  Development 8vo,  *5  oo 

Thompson,  E.  P.     How  to  Make  Inventions 8vo,  o  50 

Thompson,  S.  P.     Dynamo  Electric  Machines.     (Science  Series  No.  75.) 

i6mo,  o  50 

Thompson,  W.  P.     Handbook  of  Patent  Law  of  All  Countries i6mo,  i  50 

Thomson,  G.  S.     Milk  and  Cream  Testing I2mo,  *i  75 

—  Modern  Sanitary  Engineering,  House  Drainage,  etc 8vo,  *3  oo 

Thornley,  T.     Cotton  Combing  Machines 8vo,  *3  oo 

Cotton  Spinning.     8vo. 

First  Year *i  50 

Second  Year *2  50 

Third  Year *2  50 

Thurso,  J.  W.     Modern  Turbine  Practice 8vo,  *4  oo 

Tidy,  C.  Meymott.     Treatment  of  Sewage.     (Science  Series  No.  94.).  i6mo,  o  50 

Tinney,  W.  H.     Gold-mining  Machinery 8vo,  *3  oo 

Titherley,  A.  W.     Laboratory  Course  of  Organic  Chemistry 8vo,  *2  oo 

Toch,  M.     Chemistry  and  Technology  of  Mixed  Paints 8vo,  *3  oo 

Materials  for  Permanent  Painting I2mo,  *2  oo 

Todd,  J.,  and  Whall,  W.  B.     Practical  Seamanship 8vo,  *7  50 

Tonge,  J,     Coal.     (Westminster  Series.) 8vo,  *2  oo 

Townsend,  F.     Alternating  Current  Engineering 8vo,  boards  *o  75 

Townsend,  J.     lonization  of  Gases  by  Collision 8vo,  *i  25 

Transactions  of  the  American  Institute  of  Chemical  Engineers.     8vo. 

Vol.     I.     1908 *6  oo 

Vol.    II.     1909 *6  oo 

Vol.  m.     1910 *6  oo 

Vol.  IV.     1911 *6  oo 

Traverse  Tables.     (Science  Series  No.  113.) i6mo,  o  50 

morocco,  i  oo 
Trinks,  W.,  and  Housum,  C.    Shaft  Governors.     (Science  Series  No.  122.) 

i6mo,  o  50 


D.  VAN  NOSTRAND  COMPANY'S   SHORT  TITLE  CATALOG    27 

Trowbridge,  W.  P.    Turbine  Wheels.     (Science  Series  No.  44.) i6mo,  o  50 

Tucker,  J.  H.     A  Manual  of  Sugar  Analysis 8vo,  3  50 

Tumlirz,  0.     Potential.     Trans,  by  D.  Robertson I2mo,  i  25 

Tunner,  P.  A.     Treatise  on  Roll-turning.     Trans,  by  J.  B.  Pearse. 

8vo,  text  and  folio  atlas,  10  oo 

Turbayne,  A.  A.     Alphabets  and  Numerals 4to,  2  oo 

Turnbull,  Jr.,  J.,  and  Robinson,  S.  W.     A  Treatise  on  the  Compound 

Steam-engine,      (Science  Series  No.  8.) i6mo, 

Turrill,  S.  M.     Elementary  Course  in  Perspective 12  mo,  *i  25 

Underbill,  C.  R.     Solenoids,  Electromagnets  and  Electromagnetic  Wind- 
ings  I2mo,  *2  oo 

Universal  Telegraph  Cipher  Code i2mo,  i  oo 

Urquhart,  J,  W.     Electric  Light  Fitting I2mo,  2  oo 

Electro-plating I2mo,  2  oo 

Electrotyping i2mo,  2  oo 

Electric  Ship  Lighting I2mo,  3  oo 

Usborne,  P.  O.  G.    Design  of  Simple  Steel  Bridges 8vo,  *4  oo 

Vacher,  F.  Food  Inspector's  Handbook I2mo,  *2  50 

Van  Nostrand's  Chemical  Annual.  Second  issue  1909 i2mo,  *2  50 

Year  Book  of  Mechanical  Engineering  Data.  First  issue  1912 . . .  (In  Press.) 

Van  Wagenen,  T.  F.  Manual  of  Hydraulic  Mining i6mo,  i  oo 

Vega,  Baron  Von.  Logarithmic  Tables 8vo,  half  morocco,  2  oo 

Villon,  A.  M.  Practical  Treatise  on  the  Leather  Industry.  Trans,  by  F. 

T.  Addyman 8vo,  *io  oo 

Vincent,  C.  Ammonia  and  its  Compounds.  Trans,  by  M.  J.  Salter ..  8vo,  *2  oo 

Volk,  C.  Haulage  and  Winding  Appliances 8vo,  *4  oo 

Von  Georgievics,  G.  Chemical  Technology  of  Textile  Fibres.  Trans,  by 

C.  Salter , 8vo,  *4  50 

Chemistry  of  Dyestuffs.  Trans,  by  C.  Salter 8vo,  *4  50 

Vose,  G.  L.  Graphic  Method  for  Solving  Certain  Questions  in  Arithmetic 

and  Algebra.  (Science  Series  No.  16.) i6mo,  o  50 

Wabner,  R.  Ventilation  in  Mines.  Trans,  by  C.  Salter 8vo,  *4  50 

Wade,  E.  J.  Secondary  Batteries 8vo,  *4  oo 

Wadmore,  T.  M.  Elementary  Chemical  Theory I2mo,  *i  50 

Wadsworth,  C.  Primary  Battery  Ignition i2mo,  *o  50 

Wagner,  E.  Preserving  Fruits,  Vegetables,  and  Meat i2mo,  *2  50 

Waldram,  P.  J.  Principles  of  Structural  Mechanics i2mo,  *3  oo 

Walker,  F.  Aerial  Navigation 8vo,  2  oo 

Dynamo  Building.  (Science  Series  No.  98.) i6mo,  o  50 

Electric  Lighting  for  Marine  Engineers 8vo,  2  oo 

Walker,  S.  F.  Steam  Boilers,  Engines  and  Turbines 8vo,  3  oo 

Refrigeration,  Heating  and  Ventilation  on  Shipboard I2mo,  *2  oo 

Electricity  in  Mining 8vo,  *3  50 

Walker,  W.  H.  Screw  Propulsion. 8vo,  o  75 

Wallis-Tayler,  A.  J.  Bearings  and  Lubrication 8vo,  *i  50 

Aerial  or  Wire  Ropeways 8vo,  *3  oo 

Modern  Cycles 8vo,  4  oo 

Motor  Cars 8vo,  i  80 

Motor  Vehicles  for  Business  Purposes 8vo,  3  50 


28     D.  VAN   NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG 

Wallis-Tayler,  A.  J.    Pocket  Book  of  Refrigeration  and  Ice  Making.  i2ino,  i  50 

Refrigeration,  Cold  Storage  and  Ice-Making 8vo,  *4  50 

Sugar  Machinery i2mo,  *2  oo 

Wanklyn,  J.  A.     Water  Analysis 12210,  2  oo 

Wansbrough,  W.  D.    The  A  B  C  of  the  Differential  Calculus i2mo,  *i  50 

Slide  Valves , I2mo,  *2  oo 

Ward,  J.  H.     Steam  for  the  Million 8vo,  i  oo 

Waring,  Jr.,  G.  E.     Sanitary  Conditions.     (Science  Series  No.  31.).  .i6mo,  050 

Sewerage  and  Land  Drainage : *6  oo 

Waring,  Jr.,  G.  E.    Modern  Methods  of  Sewage  Disposal 12 mo,  2  oo 

How  to  Drain  a  House 12010,  i  25 

Warren,  F.  D.     Handbook  on  Reinforced  Concrete I2mo,  *2  50 

Watkins,  A.    Photography.     (Westminster  Series.) 8vo,  *2  oo 

Watson,  E.  P.     Small  Engines  and  Boilers I2mo,  i  25 

Watt,  A.     Electro- plating  and  Electro-refining  of  Metals 8vo,  *4  50 

Electro-metallurgy i2mo,  i  oo 

The  Art  of  Soap-making 8vo,  3  oo 

Leather  Manufacture 8vo,  *4  oo 

Paper-Making 8vo,  3  oo 

Weale,  J.     Dictionary  of  Terms  Used  in  Architecture i2mo,  2  50 

Weale's  Scientific  and  Technical  Series.     (Complete  list  sent  on  applica- 
tion.) 

Weather  and  Weather  Instruments I2mo,  i  oo 

paper,  o  50 

Webb,  H.  L.     Guide  to  the  Testing  of  Insulated  Wires  and  Cables. .  i2mo,  i  oo 

Webber,  W.  H.  Y.     Town  Gas.     (Westminster  Series.) 8vo,  *2  oo 

Weisbach,  J.     A  Manual  of  Theoretical  Mechanics 8vo,  *6  oo 

sheep,  *7  50 

Weisbach,  J.,  and  Herrmann,  G.     Mechanics  of  Air  Machinery 8vo,  *3  75 

Welch,  W.     Correct  Lettering (In  Press.) 

Weston,  E.  B.     Loss  of  Head  Due  to  Friction  of  Water  in  Pipes  . .  .i2mo,  *i  50 

Weymouth,  F.  M.     Drum  Armatures  and  Commutators 8vo,  *3  oo 

Wheatley,  O.     Ornamental  Cement  Work (In  Press.) 

Wheeler,  J.  B.     Art  of  War I2mo,  i  75 

Field  Fortifications Z2mo,  i  75 

Whipple,  S.     An  Elementary  and  Practical  Treatise  on  Bridge  Building. 

8vo,  3  oo 

White,  A.  T.     Toothed  Gearing i2mo,  *i  25 

Whithard,  P.     Illuminating  and  Missal  Painting I2mo,  i  50 

Wilcox,  R.  M.     Cantilever  Bridges.     (Science  Series  No.  25.) i6mo,  o  50 

Wilda,  H.     Steam  Turbines.     Trans,  by  C.  Salter I2mo,  i  25 

Wilkinson,  H.  D.     Submarine  Cable  Laying  and  Repairing 8vo,  *6  oo 

Williams,  A.  D.,  Jr.,  and  Hutchinson,  R.  W.     The  Steam  Turbine (In  Press.) 

Williamson,  J.,  and  Blackadder,  H.  Surveying 8vo,   (In  Press.') 

Williamson,  R.  S.     On  the  Use  of  the  Barometer 4to,  15  oo 

Practical  Tables  in  Meteorology  and  Hypsometery 4to,  2  50 

Willson,  F.  N.     Theoretical  and  Practical  Graphics 4to,  *4  oo 

Wilson,  F.  J.,  and  Heilbron,  I.  M.     Chemical  Theory  and  Calculations. 

i2mo,  *i  oo 

Wimperis,  H.  E.     Internal  Combustion  Engine 8vo,  *3  oo 

Primer  of  Internal  Combustion  Engine I2mo,  *i  oo 


D.  VAN  NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG     29 

Winchell,  N.  H.,  and  A.  N.    Elements  of  Optical  Mineralogy 8vo,  *3  50 

Winkler,  C.,  and  Lunge,  G.     Handbook  of  Technical  Gas- Analysis. .  .8vo,  4  oo 

Winslow,  A.     Stadia  Surveying.     (Science  Series  No.  77.) i6mo,  o  50 

Wisser,  Lieut.  J.   P0    Explosive  Materials.     (Science   Series  No.   70.). 

1 6 mo,  o  50 

Wisser,  Lieut.  J.  P.    Modern  Gun  Cotton.     (Science  Series  No.  89.)  i6mo,  050 

Wood,  De  V.     Luminiferous  Aether.     (Science  Series  No.  85.) ....  i6mo,  o  50 
Woodbury,  D.  V.     Elements  of  Stability  in  the  Well-proportioned  Arch. 

8vo,  half  morocco,  4  oo 

Worden,  E.  C.     The  Nitrocellulose  Industry.     Two  Volumes 8vo,  *io  oo 

Cellulose  Acetate 8vo,  (In  Press.) 

Wright,  A.  C.     Analysis  of  Oils  and  Allied  Substances 8vo,  *3  50 

Simple  Method  for  Testing  Painters'  Materials 8vo,  *2  50 

Wright,  F.  W.     Design  of  a  Condensing  Plant I2mo,  *i  50 

Wright,  H.  E.     Handy  Book  for  Brewers 8vo,  *5  oo 

Wright,  J.    Testing,  Fault  Finding,  etc.,  for  Wiremen.     (Installation 

Manuals  Series.) i6mo,  *o  50 

Wright,  T.  W.    Elements  of  Mechanics 8vo,  *2  50 

Wright,  T.  W.,  and  Hayford,  J.  F.     Adjustment  of  Observations. 8vo,  *3  oo 

Young,  J.  E.    Electrical  Testing  for  Telegraph  Engineers. , 8vo,  *4  oo 

Zahner,  R0    Transmission  of  Power.     (Science  Series  No.  40.) ....  i6mo, 

Zeidler,  J.,  and  Lustgarten,  J0     Electric  Arc  Lamps 8vo,  *2  oo 

Zeuner,  A.     Technical  Thermodynamics.     Trans,  by  J.  F.  Klein.     Two 

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